According to Sky News presenter Colin Brazier, childhood is not a happy place if you are an only child. Writing in his new book Sticking Up For Siblings, he claims that children growing up without a brother or a sister will develop language skills later and have less emotional intelligence than those who enjoy the company of siblings.
And Colin has more bad news; according to his research, only-children tend to do less well at exams and are more likely to suffer from childhood obesity.
Apparently the lack of siblings equates to less time running around outside and burning calories.
Only-children are also more likely to be prone to depression and food allergies.
Some parents say they can only afford to bring up one child. But Colin, who has six children under the age of 14 with his wife Jo, argues that larger families are often not as expensive as people believe.
He said: "There are many contraceptive forces behind the 10% rise, in the space of a generation, in the number of mainly middle-class British parents having only one child. The housing market, expensive childcare, lost career momentum.
"Our only-sibling subsidy – child benefit – has been capped for all and axed for many.
"But although want of cash is a real disincentive, for the nearly two-thirds of first-time parents who say they cannot afford family expansion, want of accurate information may also be a factor."
Colin teamed up with Swedish researcher Therese Wallin to investigate whether having more children really was more expensive.
They found the average cost of having a child fell with every extra birth, with hand-me-down clothes and toys, heating and bath water being shared, and sibling discounts for theme park tickets and schooling helping to keep costs of parenting down.
Expensive or not, what about those claims as to the human cost of being an only child?
We talk to four well-known people from Northern Ireland whose childhood was spent without siblings.
Pete Snodden (33) is a Cool FM DJ and lives in Bangor with wife Julia, who is training to be a classroom assistant, and their daughter Ivanna (2). He says:
It never bothered me being an only child when I was growing up - I didn't feel any different to anyone else. I never had any trouble making friends with children. When we went away on holidays I would be straight over getting to know other kids as soon as we got there.
Although I never particularly wanted a brother or sister I do remember that I used to ask my parents why I didn't have one. I was always told that's just the way it is.
I don't think I was spoiled but I was certainly well looked after. I didn't get absolutely everything I wanted but my parents were good to me and would have given me the shirts off their backs if I had needed them to do so.
Now that Ivanna has come along, though, I understand that completely - I would give her the shirt off my back if she needed it.
My mum always used to say that she was glad she had a son for my dad. She wanted us to be able to kick a ball around the park and go for a pint. Having said that, I was, and still am, very close to both of my parents. I don't know if that's because I was an only child and all the focus was on me.
I played quite a lot of sport when I was at school but that was because I wanted to - I wasn't pushed into it by mum and dad.
I also ended up playing records for a living because I'm actually a failed musician at heart and mum and dad never had to push me in that direction, either.
I've always had a real passion for music and I was always able to follow that.
I certainly never wanted for company when I was growing up. I had cousins, I was friends with the next door neighbours' children and there were kids from my class living in the same street and around the corner.
I also grew up in the 1990s --there were Game Boys and computer games but only four channels on TV and no internet. Being outside was much more fun. My wife Julia has siblings and she has always had a really close relationship with her parents too so I don't think it matters how many children there are in a family. I wouldn't want to have six or seven children because there's only so much of you to go around and I know that I want to give Ivanna as much of me as I can.
If we're blessed with one or two more children, though, we would be very happy with that."
Pete Snodden is on Cool FM each weekday between 1-4pm
Naomi Long (41) is the Alliance MP for East Belfast, where she lives with her husband Michael, a dentist. She says:
I never objected to being called an only child but I didn't like being called a lonely child, as some people did.
I think I was destined to be an only child as my parents married late - mum was 40 and dad was 50 when they had me. My dad died when I was 10 so when I was growing up it was just me and mum.
I wasn't lonely, though. I have a lot of cousins so there were always people around for me to play with - my aunt had kids a year older and a year younger than me so it helped that they were also my age group.
I think being an only child helped to develop my language skills - I spent more time talking to grown-ups so I developed fast. I also learned how to make friends quickly - because if I didn't make friends there was no-one to play with. I think it's given me more confidence and social skills instead of less - I wouldn't be able to do my job if that wasn't the case.
I don't think I was spoiled growing up but it's all relative - because there was only me there was more for me, but mum and dad didn't have a lot of money so there was never a huge amount for me in the first place. My dad worked in the shipyard until he died and mum worked part-time for Save The Children after I started school.
I was never deprived, though, and I wasn't pushed. Mum always made sure I did my homework and I went to Brownies and Guides but I didn't have extra music lessons or language lessons. Neither of my parents went to university, however, so naturally my mum was over the moon when I got my degree."
Zara Beggs (23) is a partner in the Candy Plum Boutique in Hillsborough and one of the organisers of Polo In The City, which takes place this Saturday in Belfast. She says:
I was never lonely growing up and I didn't have any imaginary friends either. In our house I did get all the attention but it was in the right way.
Mum and dad gave me plenty of encouragement when it came to school and pasttimes but I didn't feel pressured. Most of the time I was allowed to find my own way anyway – if I wanted to do something it was up to me. Everything was my choice.
I was probably a bit spoiled but it never reached ridiculous proportions. I started working in hospitality from the age of 14 so I was aware of the value of money from a young age. It wasn't a case of asking my parents for whatever I wanted and just being handed it. If I wanted to go to the cinema with my friends I would pay for it out of my own pocket.
Admittedly I probably used my only-child status as a bit of a bargaining tool when I was in my teens. Lots of my friends would have had older brothers and sisters to pave the way for them to go out at night but I didn't have anyone ahead of me, negotiating that territory. Consequently, I often argued with mum and dad that so and so was able to go to a place because their brother or sister had been there or was going too.
There was always family around when I was growing up. I don't have a massive extended family but we are a close one so I had the company of relatives too. It's not as if there were just three people in the house all the time.
I think I have a better bond with my parents because I was an only child. I still live with them and we run the business together – I don't think many people could work so closely with their parents. I still need my own space, of course, and I have my own social life. I've never had any trouble with relationships or making friends. Given that we own a clothes shop I deal with people every day and I've never had any trouble relating to them."
Polo in the City takes place at Lower Botanic playing fields on Saturday, August 31, to raise funds for Mencap. Tickets, £65, are available from www.mencap.org or by contacting Candy Plum. Candy Plum, Main Street, Hillsborough, tel: 028 9268 3273
DJ Hix AKA Dermott Hickey is a DJ who has recently appeared at Belsonic and has a regular show on Cool FM. He lives in Belfast with his wife Olivia, a teacher. He says:
I never minded being an only child, in fact, I never even thought about it. It never even occurred to me that having no brothers or sisters was an unusual thing. It's said that only children can be spoiled but I genuinely don't believe I was – Olivia and my friends also agree with me on that.
I tended to get everything I asked Santa for, but I wasn't the sort of child who went overboard with a massive list. Although dad used to be a decorator they have both been ballroom dancing for years. I was very active at school – mum and dad certainly introduced me to lots of things such as drama and dancing, but continuing on with them was my choice. If I hadn't wanted to take part in something I wouldn't have been made to do so. Olivia and I do intend to start a family – we plan to have more than one but certainly less than a football team.
Olivia has four sisters and she doesn't want a massive brood either so I don't think the number of children you yourself wants is dictated in any way by your own background.
I know some people say that it's tougher for only children when their parents get older and perhaps need more support, but thankfully at the moment I have no concerns about looking after mum and dad, not least because they're very independent. They wouldn't come to me and ask for help unless it was urgent – they barely even tell me if they're sick.
If I was needed, though, I would step up immediately."
DJ Hix presents Cool FM every Friday from 4pm. He also hosts The Urban Hour, Sunday, 9pm
Colin Brazier (45) worked in newspapers and for the BBC before joining Sky News in 1997. He has broadcast from war zones in Baghdad and Israel and conducted high-profile interviews with US Secretary of State Condoleeza Rice and the late Colonel Gaddafi.
He is married to Jo and they have six children – Katharine, Constance, Gwendolyn, Agnes, Edith and John. It was his large family that prompted him to embark on research into the cost of having children.
In 2009, after the removal of a lump from his forehead, he was diagnosed with non-Hodgkins Lymphoma and received radiotherapy treatment.
In 2012 his wife Jo, former head of foreign news of Sky TV, was diagnosed with stage three breast cancer at the age of 50. She has undergone a mastectomy and chemotherapy.
Colin has published his book, Sticking Up For Siblings, to debunk the myth that having a large family is too expensive.
In research he undertook with Therese Wallin he discovered the more children a family has, the lower the cost of each consecutive child. He maintains that children share heat, light and bedrooms – what does for one will do for three. The costs of clothes and toys are reduced as items are handed down.
Brazier's research shows that large families can obtain discounts on everything from hotel rooms to private school fees. Brazier also maintains that children with siblings are less likely to develop allergies, obesity and depression – running around with brothers and sisters expends energy and reduces calorific intake.
He also concludes that those with older brothers and sisters cannot coerce them into submission so they must become natural diplomats and learn to communicate through oral persuasion.
Sticking Up For Siblings by Colin Brazier, Civitas, £8