I wish I was in your position ("similar" situation but no interest from bfamily). If they are a normal close knit family why wouldn't you want you child to know them? It might be your DD's healthiest connection to her biological family and this important component of self.
When your DD is older she may identify with the issue of addiction and without healthy bio family members to relate and refer to may identify with this one small aspect of her history.
If they are dangerous, messed up emotionally or whatever I can understand but if and when I'm in your position I'm going to rally all the healthy, interested bfamily members I can!
Good luck!
