Overly affectionate 8 yr old boy!

I know this post has nothing to do with being pregnant. I just need some advice because this has been bothering my husband and I for awhile now. My 8 yro step son has become very affectionate with my husband and his grandpa over the past 4-5 months. He is constantly wanting to hug or be sit with my husband and it seems like he says I love you dad every 10 minutes. He doesn't do this with anyone else, even his own mother. He has never done this in the past so it is weird to us that he has picked up this new habit. My husband isn't a very affectionate person and never really has been. It's just how he is and it's fine with me. I think it just bothers us because it's only with men that he acts this way. Has anyone ever experienced anything like this before or have a clue what would cause him to all of a sudden act this way?