It's done in some European countries - they just had to change the laws a little bit (and to wait, until conservatives were in opposition and the the courts give their okay [:"Germany's Federal Constitutional Court cleared the way for legal same-sex marriages when it dismissed efforts by conservative governed states to block a new law.].):
2000-DEC-19: Netherlands: Gay and lesbian Dutch couples can now marry and adopt with the full privileges enjoyed by heterosexual married couples. This is the first country in recent history to have legalized gay and lesbian marriages.
2001-JUN-4: Canada: Gay and lesbian couples in the province of Nova Scotia now have most of the rights of heterosexual married couples, with the exception of adoption.
2001-AUG-2: Germany: Gay and lesbian couples may register their partnerships, obtain the same inheritance rights as married couples, and may share the same last name. Some rights are still withheld
2002-SEP: Zurich, Switzerland: Same-sex couples can now register with the government and obtain all of the legal rights as opposite-sex married couples.
In predominantly Catholic Portugal, same-sex couples who have lived together for more than two years recently were granted the same rights as heterosexual couples in common-law marriages. [Couldn't find the date, but have been in 2001.]
Phoenix32890 wrote:As long as the couple is bound by the same responsibilities as in a heterosexual union, I see no problem with it!
A marriage (or a registration) isn't only giving responsibilties but benefits, too.