If he agrees to make the change to both of your names, go with it, don't let your nagging feelings ruin it by doubting him. It would be nice if he was ok with letting you keep your surname, but I'm sure your unwillingness is giving him nagging feelings that he probably feels would screw everything up if he talked about them, like a lack of commitment from your side. If you want to cause a giant rift in your relationship bring that up to him, tell him you don't trust him or believe he's being honest. If he's willing to compromise by changing his name like you change yours, be happy about it. Your negative feelings could be feeding his. If one of you are having negative feelings going in to this, it's not going to go well for both of you.
Them's my 2c, probably not worth the cheap metal they are stamped with.
As for me, I don't like my surname. I have nothing to do with my dad's side of the family, I haven't seen or heard from anyone on his side in around 20 years. And I don't like the way the name rolls off my clumsy tongue. I've been wanting to change it to my mom's maiden name, but I'm to lazy to jump through all the necessary hoops. If I were to get married I'd gladly change my last name to hers, unless it was worse, in which case we could both change it to something better.
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The world under heaven, after a long period of division, tends to unite; after a long period of union, tends to divide. This has been so since antiquity.
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