In no way are either of them a third 'parent'. This idea that grandparents and aunts and uncles can actually be a third parent has to die. No one who actually lives in these situations is confused as to who's who.
We lived with my grandparents as children and while again, we loved them very much and they watched and cared for us like parents... The relationship is fundamentally different.
Not generally. But creating a child necessarily involves creating a stable biological relationship primarily with two other people.
Most people across history think the biological circumstances that bring us into the world are spiritually important and making the triangle between mother-father-child healthy is good for children.
For better or worse, people care their genetic material. We can either choose to create a society that makes the best of this, or we can try to suppress it and convince people that it doesn't matter.
And yes I know that surrogacy exists. But that's a side argument that opens up a lot more questions and I don't think it really changes the fundamentals.
I'd much rather see policies towards solving these problems versus one that has the government getting in the middle of my marriage or parenting.
If three-parent scenario is tried at a larger scale and if it works with small tweaks to our social contract, then why not?
Alloparenting is great, but 3 parents running the same household would be a nightmare in most cases.
The ideal would be for municipally owned mid-rise apartments in mixed-use neighborhoods to become common. Vienna does this very well, but public housing has been demonized in America (and, like the lazy dad who does a chore so badly they never get asked to do it again, our federal government starved public housing support so badly that most Americans think of it as an intrinsically horrific way to live).
I understand that in Japan there is a set of federally defined zoning types. Some beaurocrat checks your proposal against the requirements of the zone you want to build in and you get your permit or rejection within days. It's difficult to comprehend the massive impact it would have for permitting to go from an expensive, multi-year dice roll to a mostly predictable process that takes days.
Multigenerational households are another popular option to deal with economic challenges.