There is research (that I won't find now, I am busy) that families with natural born sons (not girls, for some unknown reason) have much lower divorce rates too, and across several cultures, suggesting it is something biological.
This of course, is not possible in a homosexual couple... But I think that beside that, there are several other biological systems to ensure a heterosexual couple reproduces and take care of their child until it can reproduce too.
But you should also context that the studies are based on Norway and Sweden, and the latest reference in it is from 2003 whereas public acceptance has changed quite a bit in ten years, especially in the U.S. where it seems every three months gay marriage is legal in another state.
https://same-sex.web.ined.fr/WWW/04Doc124Gunnar.pdf
EDIT to reply below:
There is research (that I won't find now, I am busy) that families with natural born sons (not girls, for some unknown reason) have much lower divorce rates too, and across several cultures, suggesting it is something biological.
This of course, is not possible in a homosexual couple... But I think that beside that, there are several other biological systems to ensure a heterosexual couple reproduces and take care of their child until it can reproduce too.