It was mostly used due to same-sex marriage not being available in some countries, to create a family unit, get property and inheritance rights, securing insurance benefits and allowing recovery in tort.
The motives for same-sex adult adoption much differ from those involving a minor, including those of a legal or economic nature.
[1] Adult adoption was the only means to legally recognise family relationships in countries and states where same-sex marriage was illegal.
[8] Once adult adoption takes place, inheritance rights are automatic, and no other legal instrument is needed.
[3] In a situation where the adopter is the first to die and there is an invalid will, the adoptee will "inherit to the exclusion of the adoptor's blood relatives.
Adult adoption was relatively rare in the 19th century, but continued to become more popular among same-sex couples who wished to have inheritance rights.
[3] In 1851, Massachusetts became the first state to enact an adoption statute, only with the requirement of supervision and approval from the judicial system.
During the late 1960s and early 1970s, those states that approved adult adoption simplified procedures for their accomplishments, such as (1) "elimination of provisions for investigation of the home"; (2) "elimination of the requirement that the adoptee must have lived in the home of the adopter for a specified length of time; (3) "changing of the provisions for confidentiality".
[10] State adoption legislation became more prevalent and started to appear more frequently after the 1860s, but it became more accepted and practised during the twentieth century.
[15] Specifically, they wished to legalise their financial relationships for "estate purposes",[7] and to care for each other when health declined.
[16] The court denied the petition, as the couple lacked a parent–child relationship, and concluded that they were attempting to use adult adoption for marriage purposes.
[1] Due to prohibitions on marriage between parents and children, same-sex couples who have been adopted by their partners will be forbidden to marry each other.
[8] The proposed 1962 version of the Model Penal Code was the first to define sexual relations between a "parent" and an "adopted child" within the definition of incest,[8] and with more than 25 states in the US in 2009 subject to statutes including that the relationship between adopted parent and child is incest, such as Texas, Tennessee, Utah, Ohio, Virginia, etc.
[9] In most states in the US in the late 1990s, the legal relationship with the adoptee's natural parents would end upon adoption between the two parties taking place.