I definitely think they should help their families out. Helping them select an alternative service is helping out.
Being on the hook for endless tech support while getting blamed for everything is not helping out. It’s also not healthy for your relationship with your sibling, and it’s not a good use of family holiday time.
A partner is different. You already share a lot of infra, and since you presumably spend a lot more time together it’s not likely to impact your relationship as much unless you go full Pat & Mat do IT.