"Biological" kids?

I found this quote that has made me think a little deeper than labels...and smile!

Like many adoptive parents, I chafe at the term “biological” to designate only my birth children. First because all children, of course, are the products of biology. Second because aren’t my children by adoption also mine biologically? We breathe each other’s air, prepare and share each other’s food, borrow each other’s combs and socks and pencils; Helen sometimes falls asleep on my bed twirling her fingers through my hair. Aren’t these somehow biological processes? Aren’t our cells intermixing? Haven’t the years of Berenstain Bears books I’ve inflicted on these children been immortalized as brain cells? --Melissa Fay Greene