The question makes no sense. Sorry, an ex? keep in contact with his ex wife of ten years family? Are you asking if it is alright that your present partner has relations with his ex-wife's family?
If that is the case....I do not find a need for concern. But, I would suggest finding out the reason for continued contact? It might be important and show him that you are concerned about this area. He might take it as a problem or see it as an opportunity? It is unknown how he will handle it, should you bring it up in conversation.