Advice for sis

Hey everyone! Today, my brother who is a couple of years older than me came out to me. I've always kind of thought he was, but I've been in denial in a way because of how unsupportive my parents are of gays. I am 100% supportive of him and didn't even blink when he told me, but my family is SO conservative. What advice could you guys give me for him on coming out to my parents? He's moving out next year and is planning on doing it when he's not under their roof. He wants us to continue being a close family, so how can he come out to them in a way that will not permanently harm their relationships? Sorry if this is dumb or anything I'm just very uninformed and I just want the best for my brother