Husband wants to legally change his name

My husband's name is Sam, but people have a nickname for him. Sunny. His step dad gave him the name. It's because he was a really happy kid and always smiling. They called him Sunny Sam. He still has that nickname. Thing is, only me a few people know my husband wasn't really that happy as a kid. He faked it a lot and tried to fake it til he made it. He was being sexually abused at home by his step brother and physically by his step mom. His step dad actually loved him and didn't know what his biological son was doing to step son and his step dad was also being abused by his mom but he stayed so he could protect my husband. His step dad died after suffering a stroke. And his mom died 4 months ago. After therapy yesterday he told me not to call him Sam anymore because it's the name is shitty egg donor gave him. He wants to go by Sunny and is starting the process to change it. what would you do if your husband told you this.

I'm asking because I don't have a problem with it, my mother was just saying no matter what your mom does she's your mom and she gave him that name and he should honor her with his name. My mom is very opinionated and I'll always support him. Just wanted opinions