Nathaniel Santos Batista Junior, a jurist who helped draft the document, said the idea was to protect their rights in case of separation or death of a partner, Globo reports.

Ms Domingues, who is based in the Sao Paulo city of Tupa, said the move reflected the fact that the idea of a "family" had changed.

"We are only recognizing what has always existed. We are not inventing anything."

"For better or worse, it doesn't matter, but what we considered a family before isn't necessarily what we would consider a family today."

But lawyer Regina Beatriz Tavares da Silva told the BBC it was "absurd and totally illegal", and "something completely unacceptable which goes against Brazilian values and morals".

Ms da Silva, who is president of the Commission for the Rights of the Family within the Institute of Lawyers, says the union will not be allowed to remain in place.

Some religious groups have also voiced criticism of the move.

While Ms Domingues has approved the union, it is not clear whether courts, service providers and private companies such as health insurance providers will accept the ruling.

【巴西一男两女家庭模式遭炮轰】相关文章：

★ 美国28%成年人依然住在父母家，其中28%没工作

★ 男性应该使用感性的表情符号吗？

★ 全职白领做兼职时应注意什么问题?

★ 如何让一个男人向你承诺

★ 关于排毒茶,你应该知道的那些事

★ 矿泉水越来越奇葩，改用易拉罐装就融资160万美元

★ 星巴克又有重大表态，男女工资必须一样

★ 宜家惹出国际问题,卖的地图少了一个国家

★ 为什么老公需要多做家务?

★ 《波西米亚狂想曲》口碑爆棚，4首经典了解皇后乐队