When a man & woman are married, many states (mine included) consider the husband to be the legal father of the child, even if the husband isn’t the biological father.
Every time you year of a father being forced to pay child support even though he isn’t the biological father this is what’s happening.
So, we already have a legal standard that says the spouse of the person giving birth is legally a parent of the child—even if they aren’t a biological parent.
That is so wrong.
A form of slavery.
So, were we to establish a law that said a child could be recognized as the parent of one of their siblings, or a child could be the legal parent of their own parents, would you be ok with it? Could we establish anything, regardless of biology, just because it is a law?
Paternity is a sticky subject. Presumptions can be overcome.
My family members know to get a DNA test no matter how much in love you are at the time. Do it in secret if you have to but do it.
Now whether they are smart enough to follow through or just too dumbstruck in love will remain to be seen