Do I have a chance of getting my niece and nephew?

As a family member you are entitled to notice and CPS should have provided it. Even if the child is placed with a foster family and has not finalized an adoption, you still have a chance to adopt your niece or nephew. You do need to contact an adoption attorney in your area, immediately, since time is of the essence. Their are many studies done on children who are placed in foster care, one of the most prominent findings is that children are better with the biological parents, and if that is not possible then with blood relatives. I do strongly sympathize with you and know how hard this can be on family. You should not give up hope, because your basic scenario has happened before with CPS and I have had clients where they do get their family member in their custody.