I suggest that judging the father is not helpful. Because the boy has several caretakers who are taking care of him CPS will not get involved. Everyone in the family is responsible for his care.
If the brothers want the father to be more involved then they need to approach this from a loving supporting way. Have they had a family meeting during which they decide who will do what? Have they looked for resources to help with his care?
I suggest that the brothers call the boy's doctor and ask for a referral to a social worker who can help find ways to make his care better. Also ask the doctor about the urine smell.
In the meantime increase his fluid intake to 8 8oz glasses/cups of fluid per day. It's my guess he's not getting enough fluids. If that doesn't get rid of the strong smell definitely consult a doctor.