I find it a little weird that it is being suggested that he needed to adopt the children to be their legal parent. People use surrogate mothers and sperm donors all the time when fertility is the issue. For example, if a man is infertile and they use a sperm donor for the wife to conceive does the man have to adopt because he is not the biological father? Or if a woman is infertile and has to use a surrogate to carry the baby does she then have to adopt the child? I never thought so, but then again I don't have any experience with this.
It just strikes me as so strange. Whether or not he is the biological father, he is the primary parent to all three of these children.