Will we loose my nephew if i call CPS?

My brother and his girlfriend have 2 kids, a boy 14 months and a girl 2 months. My brother is 22 and his GF is 20. They all live with my mom, dad and sister. My brother is off at work from 7 in the morning sometimes for 12+ hours during peak season or till about 2-3pm during off season. His GF doesn't work n is home with the kids all day. She watches television while on facebook on her itouch and downloading music on the laptop. My nephew's crib is full of diapers, dirty clothes, toys, etc and she still lays him there to sleep. Their room floor is about the same. She undresses and just steps out of her shorts and underwear, one day my mom found that under a pile of the babies clothes. she feeds him undercooked food. She will be feeding him but is so concerned with her itouch that she holds the spoon of food out n my poor little nephew holds his mouth open but she just holds it out till she's finished looking through facebook. My mom seeing this has taken on almost all responsibility over my nephew. She feeds him, bathes him, changes him, to the point where he looks for her for everything he needs. The worst was today when she went to her mom's for most of the day and when she came back, my nephew had filthy clothes on, a sweater vest (its like 95 degrees here now) diaper completely puffy full of urine and he seemed to be in pain when taking a step. This is a boy who is constantly running around but when we tried to stand him up he would cry and cry. She insisted that he was just in a bad mood because he had just woken up. My mom kept on asking her if something had happened that way we could fix it and she kept saying nothing had happened. we looked him over and no apparent injury was visible. I was ready to take him to the hospital to have him checked out but little by little he started to want to walk on his own. he still limped a little but was walking on his own a little better. When my brother got home he just said oh maybe he got a cramp, and kept on talking about his day at work and eating his dinner. I got mad that he was just so nonchalant about his kid but when his GF complains of a headache he trips over himself trying to make it better. When my mom brings to his attention stuff his GF does he defends her tooth and nail. In his eyes she can do no wrong n in the meantime she neglects the kids as she pleases. She feeds them whenever they get fussy, never has them on any type of schedule. My mom has expressed concern that she gives my nephew a lot of tylenol during the day so she can nap. I do see them giving him children's tylenol regularly. She believes this because when my nephew is upstairs with his mom he's usually asleep n very quiet. When mom brings him down with her after my brother leaves for work the baby will be up n screaming n just being a kid. She's tried to talk to my brother about it n like i said he just makes up excuses for his GF and gets upset that mom accuses her of any wrong doing. Once, they all got into a big argument and the girl said she was leaving to her mom's with the baby (one baby at that time). My brother just looked at my mom and said "see what you've done? now im going to lose my son" After today I was ready to call CPS but since mom lives in the same house, will cps remove the kids and place them with strangers in a foster home. I have heard terrible stories from places like that and im afraid. I would love to keep him myself but i work 12 hours a day- 6 days a week and he'd end up with a babysitter or my mom, again, in the same house as the mom. At this point I could care less if my brother gets mad at me or ends any relationship with me. They have taken over my mom's house and made it seem like my parents are the ones living with them. The family has no use of the living room because she is always there watching tv with baby stuff spread out over both couches. Its not fair, but we don't want the kids to go live somewhere where they will be at risk of getting seriously hurt and constantly neglected. Help!