I know there are a lot of people here who are saying "dont bring it up, let him do it". However, I want to also offer an alternative: I think you should bring it up respectfully but openly. Yes Stuttering is his thing, but it also affects you and your relationship and you have the right to address it. When I first started dating my husband/ at that time boyfriend/ 6 yrs ago, I was so scared he'd figure out that I stuttered and reject me ( I really really liked him). The anxiety was killing me and was actually preventing me from being my truest self. Eventually my speech started to get really bad coz all I could think about was NOT STUTTERING. One day after a particularly bad block that I tried to unsuccessfully hide, he asked me about it. He said "do you stutter?" I got defensive and said "sometimes". He dropped it. I felt rather embarrassed, but after some time, (like 1 day), I felt like this huge weight had been lifted off my chest. I am still super defensive about it and I dont like to talk about it to anybody but the person I feel most comfortable with is him, because he is one of the few people who knows that I still stutter at times. Most people either think I've grown out of it, or that have weird speech patterns. He's kind of my safe place now.