I told him that he needs to see if I am having an issue before assuming that I am stressed. He said that he knows how I feel and he doesn't need to ask. So, that makes this a little harder on me. My sister feels like he has internalized this and made it his thing. Maybe he has undefined internal boundaries?
I couldn't tell you since I don't know him. But I would re-iterate that asking is preferable because you are trying to learn to relaxation techniques and need to assess the situation yourself before turning to others. And I agree with Silver, you definitely need to have a calm discussion.