One would think that choosing your best man and usher is a very easy thing to do. Traditionally, your best man is your closest male relative or best paddy. Actually, your best man and usher should be that person that will be ready, willing and able to take on the responsibilities and duties, before, during and immediately after the wedding.
More importantly the best man should be someone that is acceptable to your bride You really should think of making that day a happy day for the both of you. Ushers generally are chosen from both sides of the family but can quite acceptably be a group of friends.