About 16% of gay and lesbian parents have no legal status over their children, research has found.
The new study also revealed almost half of all lesbian, gay, bisexual and transgender (LGBT) families have experienced discrimination in the past five years.
Campaigners have called on the Government to make changes in the legal system for LGBT parents and for policies to reflect family diversity. Couples also need better access to reproduction services, while parents and their children must be given better support, they said.
Patrick Stoakes, programme director of LGBT Diversity, said the report will be a vital contribution to understanding the diverse family relationships that exist in modern Ireland.
"We hope and believe that it will provide policymakers and service planners, as well as groups that support parents and families and LGBT communities, with a sound basis to promote greater inclusion," he said.
A total of 153 LGBT people who had 272 children, and 170 adults actively planning on becoming parents, took part in the first ever study into LGBT parents in Ireland by Dr Jane Pillinger and Paula Fagan. They found 51 of the children are being parented by an individual who had no legal authority over them, despite having an active parenting role.
One gay father revealed his partner was not allowed to collect their children from school and was not allowed to give them a sick note.
"Their mother's (opposite-sex) partner was not put in the same position when something similar happened," he added.
More than two-thirds of participants were the biological parent, with half becoming a parent through a previous heterosexual relationship, and 40% had a child through other pathways, such as assisted human reproduction. A small number had also fostered (7%), adopted (7%) or undergone surrogacy (5%).
However, the study found that more than two out of five would-be parents did not know what their legal status would be when the child was born. Elsewhere, a third planned to be a joint legal guardian and 19% wanted to be a joint adoptive partner - even though there is no legal means for anyone other than a biological parent to be granted guardianship.