Should I call CPS on my sister?

My 2 year old nephew has been staying with me and my husband for 3 months now. His mother is in CA "getting her life together" and his father is in and out of jail in TX. TX is both theirs and my nephews current residence. Although he is staying with us in LA. Last night my sister tried to kill her self again. She is on lockdown for 72 hrs. My sister was supposed to sign him over temporarily before she left for CA but never did. So we're basically just paying for him. She let his medicaid expire and we can not get him on our insurance unless we have custody. Neither of them are fit parents which is why he has been staying with us. If I call CPS will they come here and take him from us and take him back to TX to put him in a foster home? Or will they keep him here with us? I don't want to call unless I know he will be able to remain with us... I just want to do something to relinquish her rights immediately. I'm planning on talking with a lawyer next week but want something done now. Its been this way since she was pregnant with him.