bridal party questions

I agree with what you're doing. I see his point about your brother but it's traditional for ushers to be part of the party but not people doing readings. I wouldn't ever consider having sil as a bridesmaid

It's up to you who you have My bridesmaids are my friends and my family, non of my fiance's side as he isn't really close to them, and i don't know them that well.
It's really up to you guys, don't let people persuade you to have people you don't want.

Not at all, I'm not even having my sister as we r not close, I made the choice that I would prefer to be surrounded by people that would actually support me over keeping people happy!!

If your H2B has actually officially made your brother an usher, then I don't see a problem. If you're just kind of trying to squish him into things, then that's a different matter.

My OH wanted me to have his 2 sisters as BMs so I agreed, and he had my brother as an usher. TBH they didn't really help out very much, but it was nice to include them.

As others have said if your OH has chosen to have your brother as an usher then that's fine, but if you are just pushing for him to be one, then you should have OH's sister as a BM too really. You say you aren't that close to his sister; well is OH any closer to your brother to want him as an usher? Would it be a nice opportunity to get closer to his sister? Its between you and your OH really - so you need to agree what you think is fair for both of you.

Traditionally the groom chooses the ushers and the bride chooses the bridesmaids.

However my brothers were ushers but my SILs weren't bridesmaids. I love my SILs but I already had 4 adult bridesmaids. We asked one SIL to do a reading and the other to be a witness.

H already had two best men but had too many other friends to pick a few to be ushers so it worked out quite well having my brothers even though H and them aren't close as they don't like anywhere near us.

I think it depends how close you all are. As already mentioned, how close is your OH to your brother? if they aren't that close then it's a lovely gesture of him to ask your brother to be his usher (has he? you didnt say?), and therefore I might be nice if you did the same for his sister. Perhaps it would be a great opportunity to get to know each others siblings a bit better?
However, its entirely your choice and your bms are there to support you and if you think who you've chosen will better do that then perhaps stick with that. Have you spoken to your OHs sister, would she like to be a bridesmaid? she may not want to anyway if your not close.

For my bms I have my sisters and OHs sister, who im close to. My best friends are having other roles (readings witnesses etc) OH is having his best mate as best man and my brother, his cousin and other friend as ushers, but OH and my bro are quite close.