Is it wrong or selfish for me to fight to keep a family members baby?

I was asked to take care of a family members baby because the baby was placed with DCF and they wanted the child to be in a kinship placement. The mother also has three other children that are presently with her. The problem is that she has a hard time taking care of all of her children, she is always yelling at them and is not a very clean person and is partying and drinking and doing drugs while the children are in the home. She and her boyfriend are both under investigation and are supposiably trying to get clean so they can have the baby back. I have been told that this is all a show in order to get the baby and as soon as the baby is back with them they have said that they will go back to their ways again. I love my family member and would like to see her become a good mother and be able to care for this child right, but I love the child to and need to put the childs needs first. I'm just really confused about how I should be feeling.