His best friend in high school was hearing impaired and he learned to communicate with him using ASL though he says he’s a little rusty now. I think the same friend encouraged him to get into acting when he was about 15 years old.
Not about being deaf but…
When I go to conventions I carry a totoro named Percy around with me. A few years ago we got the chance to meet Tom Hiddleston, Sebastian Stan, Anthony Mackie, Chris Hemsworth and Chris Evans. When I went in for the picture, I was a little off because my wife wasn’t with me so I sort of stammered out asking the guys to hold Percy while I found a place to stand. (I’m 5’4, everyone was bigger than me) Sebastian recognized him from 2014 when he almost signed it and we got this amazing picture:
So he wanted to hold Percy and all but snatched him from my hands. Anthony Mackie was like a child going “totoro totoro!” And snatched it from him declaring HE was going to hold it and after a few seconds of this, Chris Evans grabbed it, put Percy in his lap like he was their dad taking away a favored toy. It was the best Captain America moment ever. I can’t find the picture for some reason but it’s cute as hell