Can a member of your family working in law enforcement investigate another member of their own family in a criminal investigation?

It is well within the rights of a law enforecement officer to perform a criminal investigation of a family member. That officer would have to follow the same ethical rules similar to any other case. However, often times a officer can ask to be reassigned if it appears that there may be a conflict of interest that may call his or her ethics or ability to perform justly and lawfully into question.