You should have no issues. Your setting it in contacts correct? This should be your phone contact. There would be an entry for him, then you expand it and there should be a ring tone option. Also make sure you only have his number in there once. So like say your importing your contacts from Gmail. You may have him twice in there. Like once for a contact called dear hubby and then again under a contact called home. Maybe you added hisome cell there cause well when you call home you have your cell so you want it to ring his. If so set this ring tone too to be the same. Everywhere his number is needs to have same ring tone. So check if you have his number more than once.
Also if you have your home number as his home number this could be confusing contacts try updating his contact so it only has his cell