I don't think it is fine. Tax breaks were meant for married couples raising children. This crap about siblings, friends, etc is a farce. What if one has more than one sibling or both parents are still living?
You're argument leads to legalized civil polygamy.
Pretty soon nobody will be paying their "fair"* share of taxes.
*N.B. I don't think the current progressive tax system is fair.
Well, I don’t think the current progressive system is right, either. However, the point I was making is that it originally had nothing to do with sex, but was purely about making life easier for households where the two principals weren’t a married coup,e. IIRC, it gave them some automatic legal rights, such as hospital visitation, too,
The problem is that the gays took it over and made it sound like it was all about them, which is why it never got off the ground and now they’re trying to take over marriage. And forget about all those other households that would have benefitted.