Agreed up to the bloodline.
My wife doesn't know all of my exes names. My son doesn't even know I've had other relationships (he's 5).
I know my dad had 1 girlfriend before my mom (only because I once saw an old picture of him and the ex together). I have no idea how many relationships either of my parents have had, and they didn't even say that ex's name. This isn't really something I've talked about with anyone before, but it seems to be natural to not tell the kids about that.
How would one even go about to pass this down to their kids? "Bee Tee Dubs, kids, your mom is actually my second love...."