Advice on custody?

Ok my last question went raw because of my lack of detail, so i will try hard to make this make sense. my husband and his ex were never married but had two children, one in which is not biologically his but he took on responsibilty of. so in our eyes that his child. she has always been challenging in some ways. she's been through some rough things. but in turn she took his kids away and he has been trying to get money to get a lawyer. unfortuntaly we've had some life problems thrown our way and has us up to our ears in bills. we've been trying though and it's been a few years. this isn't a point of him being a dead beat dad or anything and his ex understands what she did by taking his kids from him. she's paying and hes been paying all along by not getting to see them. he's been following up with the agency or whom ever deals with child support and because she never followed up for it, they never took his money. she said it wasn't right because she wasn't allowing him to see his kids.