Note: me and my fiance get along really well with everything else, but we've just had a disagreement with this.
He wears his late brother's wedding ring on his right hand, and his brother's necklace. I can get behind the ring because you don't really notice it as much, but the necklace is more noticeable. It has his brother's, brother's wife and their daughter's initials engraved on it.
I asked him if he'd take off the necklace just for our wedding day. I also have a necklace I got as gift from my mom that I'm not wearing on the day because it doesn't go with my dress. It's just one day and he can wear the ring if he wants.
My fiance refused and said it's his brother's and he's going to wear it.