Name dispute

My SO and I can't agree on a boys middle name we have chosen William for a first name which is his fathers middle name but he wants Arthur (his step-fathers middle name) and I want Philip (my recently passed fathers first name) it's really upsetting me that he wants to tribute both his dad's but not mine when he knows how much it means to me. We are still yet to pick a girls name with only 43 days until my due date