There is only one way children are produced and that is by having a biological mother & a father, simple facts of life I am sure you are aware of. If a same sex couple in a relationship have children that means the child's mother is absent by design & intent of the same sex relationship. Two dads leaves no room for mom.
This is how it practically works out when Sally has two dads mom is relegated to a peripheral role at best and at worst once her womb is used, discarded.
This whole utilitarian arraignment isn't designed to do what is best for the child, it is designed to satisfy the heterosexual procreative impulse of some gays at the expense of the child.