It looks like members of Germany's parliament will vote Friday on whether to pass a marriage equality law. What seemed unlikely a short while ago became reality when, at an event hosted by the women's magazine Brigitte on Monday, Chancellor Angela Merkel said she was not completely opposed to legislation allowing same-sex partners marriage, describing such a vote as a "matter of conscience."

The likely support from some of Merkel's more liberal Christian Democrats (CDU) representatives, along with members of the coalition-partner Social Democrats and members of the opposition Greens and the Left Party, means a law to give homosexual couples the right to marry is almost certain to pass. But the conservative  CDU has traditionally opposed gay marriage, as has its Bavarian sibling party, the Christian Social Union (CSU).

One reason for such opposition - and part of a complex political and cultural landscape surrounding same-sex marriage - is that full marriage rights would likely grant homosexual couples full adoption rights as well. And opponents still believe that growing up with two parents of the same gender could harm a child's development.

Johannes Singhammer, a member of the CSU and vice president of the Bundestag, told public broadcaster Deutschlandfunk on Tuesday that "marriage for all," as it's known in Germany, "mustn't pass."

"People knew why they voted for us and what we stand for," Singhammer said. "We are against discrimination, but it's important to us that a child's well-being plays the biggest role in the adoption process."

Merkel herself admitted to a similar mindset in the last federal election campaign. During a discussion with voters in September 2013, a gay man asked the chancellor whether she was in favor of letting same-sex couples adopt.

"That's a controversial discussion," Merkel responded. "I'm unsure with respect to the child's well-being," she added.

'Children with same-sex parents grow up just as well'

Elke Jansen is a psychologist and psychotherapist. She says there's no proof that children suffer from growing up with same-sex parents and points to a representative study conducted on behalf of the German Justice Ministry in 2009.

"The results show without a doubt that children with same-sex parents grow up just as well as kids with heterosexual parents," Jansen, who's also the manager of the German Gay and Lesbian Association's Rainbow Families project, told DW. "They have a good sense of autonomy, but still share a close emotional bond with their parents. What's surprising is that kids in rainbow families even have higher self-esteem on average than kids who grow up with a mother and a father."

A majority of Germans are on board with equal marriage rights and have no problem with same-sex parents. A poll conducted by the German Anti-Discrimination office and published in spring 2017 showed that 75 percent of Germans are in favor of full adoption rights for homosexual couples, and 83 percent are in favor of passing gay marriage.

An antiquated argument

Despite what the general population thinks, the belief that children would need a mom and a dad so as to have mixed-gender role models has been utilized by some conservative politicians. Volker Kauder, the head of the CDU parliamentary group in the Bundestag, opposes gay marriage, deeming it "unnecessary" in March of this year. In 2013, he used the role-model argument to explain why he was against granting homosexual couples the right to adopt.

"I believe ... that it's best for children, especially boys, when they have father and mother, both elements, in their life," Kauder told ZDF.

But the notion is antiquated and has no scientific basis whatsoever.

"The idea that children passively take on whatever their parents represent is outdated," Jansen said. "Children actively look for role models and those aren't always their parents."

Cordula Lasner-Tietze makes the same point. She's the director of the "Deutscher Kinderschutzbund," or German Child Protection Agency (DKSB), one of the biggest and most well-known NGOs nationwide that advocates for children's rights.

"A child doesn't grow up removed from any kind of social environment," Lasner-Tietze told DW. "That's where they find role models, too. I know a situation where a kid's aunt is her female role model."

The family therapist also said that in German society today, a child's well-being couldn't be used as an argument against gay marriage or adoption rights for same-sex couples.

"I believe when children grow up with same-sex parents for whom the child's well-being is of the highest priority, in a family where he or she is protected, supported and heard, then those are good conditions," she said. "The sexual orientation of two adults is less important. If two people can manage that, the child will have a good start in life."