Legal Question in Family Law in California

Unless there has been some legal action terminating the parental rights of the child's biological mother, she remains responsible for both his support and his conduct. If the grandmother is providing housing for the child, ok, youth, she is also responsible for his behavior as he is technically in her home and subject to her control. My concern, as a family member, would be what is happening between the child and his mother such that he is no longer living in her home and appears to be unsupervised by his mother. You should discuss the situation with your mother and your sister and possibly even your nephew. If the family members are unwilling to take the appropriate steps to address your nephew's conduct, it may be appropriate to involve the juvenile court authorities. Hopefully there are solutions to your family's challenges that do not involve the juvenile justice system but this may also be one of the few ways to get the youth the supervision and behavior modification resources that he may require.