Sociologist Mark Regnerus discusses what we are learning about homosexual marriages, based on studies of countries that have had those arrangements for some time.
It seems lesbian relationships tend to be short, so the divorce rate for lesbian couples is very high, much higher than for heterosexual couples. Also, the frequency of sexual relationships diminishes for lesbian couples.
With gay males, adultery is almost the norm (though not for lesbians). Though married gay men have more partners, they have less sex than heterosexual husbands and wives.
Apparently, the “sameness” of the partners in same-sex marriages contributes to these effects.
Regnerus also speculates on the influence of gay marriages on heterosexual marriage, citing reasons to believe that the “monogamish” arrangements accepted among gay spouses will be emulated by married men and women.