Please help me

In May Me and my Fiancé found out we’re expecting a baby. At this time we made a bet that if it was a girl I would name her and if it was a boy he would name it. Well pass for a couple months we both talked about names before we found out .I told him I always wanted a little girl name Charlotte because it was my great grandmother’s name that had passed away. He disagreed and said that he didn’t want to older name so we agreed to move the name to middle name. Which I was not very happy about but I got over it. Went through multiple name choices and came up with the name Tatiana which we both fell in love with. That time we decided Tatiana Charlotte And his last name. So then we found out that we are expecting a little girl so we stuck with the name. Myself I have two middle names so I want to give my girl something that was from me. So while we were trying to come up with the second middle name I thought of Kay which is my aunt who raised me name. We both agreed so we named her the following Tatiana Charlotte Kay. One day while we were out shopping I received a call from my fiancé saying that his mother would like her name in Tatiana’s name. I told him I understood and I felt selfish because her name was already set. Now in July we met up with his mother in the first thing that she says is that she doesn’t like the name then later gives us an alternate name. So later that evening she asked for the full name my fiancé says Tatiana Charlotte Marie at this time I look at him crazy because this is not what we agreed upon. So tonight we decided once again to talk about her name. At the end of the day he says I need to meet him halfway and put his mothers name if I don’t he’s going to feel like I am biased and selfish. He says that the whole name is my family and not his . Me on the other hand have my heart set on Charlotte Kay as the middle name And I just don’t know what to do I understand the way he feels but at no time before his mother said anything was this a problem or was it so important to him and now it is.. Really need help