If my ex-husband says that I am required to disclose to him if I am dating/living with another person is this any of his business?

Dating, no. Living with another person, no. Living with another person WITH the minor children from your marriage to that ex-husband, yes, you should tell him.

Dating no. If the children are living with you and you move an adult in, it would probably be a good idea to advise your ex, since he is entitled to know about things that impact the kids. This would hold true, even if you are the non-custodian. If you have moved in with the boyfriend, you need to comply with the Indiana Relocation Statute.