Naming my son after his father

My husband and I have known each other almost our whole lives, and when we dated seriously we discussed children and names. What was really important to him was having his first son named after him. Now that our son is on his way I've honored his request but asked if he'd be okay giving him a middle name as well and he agrees. (Sorry this is getting long) well now my husbands sisters keep referring to our baby by the middle name we chose and its angering me because they feel our son shouldn't be a jr. So basically, should I nip all this crap in the bud and drop the middle name I wanted, or just be patient and constantly correct them.