WBWP/(Y-ad),(PA-el),(Pa-Bk)/Donated to a sperm bank
< WBWP
You donated to a sperm bank? Well, that makes perfect sense given the relationship settings. The sperm donor is not even considered the legal father in cases like this, so of course you wouldn't have had any kind of actual relationship with your child.
So then, the question is not so much how you could have a child and not have much of a relationship with them. Given these circumstances, the real question is how you even know them at all now.