how, when do i tell my 10yr, this isn't her father

Yesterday, my daughter imformed me that paternity tests done for her 10 1/2 yo daug found her dad kirk (an alias , is not her biological father. But what a twist, unbeknowst to me, it turns out that kirk, then 28, got her, then 15, drunk and allowed a friend/acquaintance to come have a one time encounter w/her. yes, i took legal action, he persuaded her not to testify, therefore he got off lightly. the child came, she looked like very much like his family, so she and kirk dismissed this other guy. However she didn't know this guy or even his first name and "kirk" has disappeared, like he so often does. kirk has somewhat attempted to be good father but has failed royally. his "daug" finds such displeasure in spending time w/him, so we don't make her anymore. But his family had doted on her since the beginning. her grandmother is loving, awesome, and adores and supports her every whim. so do his 4 siblings, cousins etc. she longs to spend every almost all her spare time w/them. i'm devastated at the mere thought of having to tell this poor child that these people are not her family and see them dissapear from her life. she will be crushed and heartbroken. i don't feel that they could continue as before w/out looking and feeling differently towards her. don't know when or if this "real" dad can be found. everyone's looking to me for guidance, i am so totally lost. If, what, when, why, and how do we tell her and his family.

[AnnieBrooke]

It almost sounds like you should not tell her or the family.  Maybe when she is 30.  A kid's family is who acts like the family, not who the DNA says is the family.