Sir Kenneth Branagh has said there is "no mystery" as to why he and his wife have no children.
The Belfast-born star of stage and screen was speaking ahead of the new series of Wallander, which he said contained some of the most difficult scenes of his career.
Sir Ken plays brooding Swedish detective Kurt Wallander as his Alzheimer's disease starts to take hold.
He said, however, that wife Lindsay Brunnock - a film art director - helped him relax during filming.
They married in 2003 after two years together in what was a quiet ceremony compared to his lavish wedding to Emma Thompson at Cliveden country house in 1989, which crowned them as UK theatre's golden couple.
They wed in the New York flat of two actors from his London and Broadway production The Play What I Wrote with just seven people present.
The actor's marriage to Thompson had ended in 1995 after he began an affair with Helena Bonham Carter during filming of Mary Shelley's Frankenstein in 1994. That relationship lasted four years, and it was Bonham Carter who introduced him to Lindsay in 1997.
Their paths crossed again in 2001 while making Channel 4 drama Shackleton, in which Branagh played the lead role. Two years later they married.
The couple do not have children, and Sir Ken told the Daily Mail: "There's no mystery. It just simply hasn't happened."
Instead, they live a quiet life in Berkshire with their dogs.
"She's like most women in that she's smarter than most men," Branagh said of his wife.
"She's certainly smarter than me and knows me better than I know myself. She understands that it's great when people love what they do, but also knows they need the right kind of balance in their life."
Wallander has battled booze, diabetes, several major crises of confidence, suspension from his job and a painful divorce.
He faces his biggest challenge yet in a new three-part series.
Branagh was determined to make the decline in health convincing and conducted his own research into Alzheimer's.
"I started off looking at it medically but then a lot of it became anecdotal from friends, friends of friends and family," he said.
"What struck me most were the stories where people had ended up in absurd situations.
"There was the father of a friend of mine, an upright and proper figure, who'd been heavily involved with his golf club. He was found wandering on the course, swearing his head off, having never sworn in his life.
'That's a tiny example of the many shades of this thing. My sympathy for people dealing with these situations is enormous. It must be challenging."