Adoption: do you really need your kids to have your DNA within them?

I was having a talk with my girlfriend the other day about having kids some day, and the subject of adoption came up.

She mentioned the idea of adopting, and I could instantly think of plenty of good arguments in favor of it.

However, while I found my self in favor of adopting, part of me still wanted “a real kid”. I was then struck by what a horrible thought that is, imagine having a father that sees one child as his child but the other as his real-deal proper child.

So, do I (or you) really have to have a child that has your actual DNA in their genetic makeup? Where does this impulse/instinct come from?

Would it be better if we all adopt until no more kids are left needing parents?

Would it be better to keep passing on our own DNA so that evolution and the gene pool don’t get stunted?