You don't owe them anything just because you share blood. That being said.
Without knowing the background: if it was not him you're mad at, he might just want to have contact with his offspring. Nothing inherently bad. So why not? Can't hurt. It's not yes or no forever. Test what he REALLY wants and decide then? At least you can never blame yourself in the future for not trying, if you're inclined to doing these things.
But if there is any toxicity at all, fuck it. Ground rule #1 in life: cut toxic people out. Period. Be it blood or stranger. Doesn't matter. But you already did this long ago, so kudos for that.