My MIL answers differently in different circumstances. I’ve known her since she was in her 50’s and it was not unusual for her to say she has 4 living sisters. Then she often would continue talking about how many she had total (although she states it including her saying we were ten children rather than saying she had 9 brothers and sisters. That might be a language thing) and then additionally sometimes she launches into how some of them died. However, keep in mind when I am with her she is usually talking to family members or very close friends.
I brought up her age only because as people get older it is less odd for someone to mention a sibling had died. Although, certainly young people lose siblings too.
My FIL always answers with how many sisters and brothers he had total. I never hear him say who has died and who is alive or how many have passed away unless he is specifically asked.
My grandmother always said she had two brothers and didn’t elaborate unless there was specific reason to. They both died fairly young. In their 30’s and 40’s.
I think it partly might also depend on whether the sibling died when you were so young you don’t remember them or didn’t know them. That’s not the case for you though. I’m sorry to hear you list your brother.