What a ridiculous question because how can anyone say for definite?
All these “my partner, always,” type responses are a bit silly as obviously it depends on the situation...
Your sister rings you because her DH has admitted he’s having an affair, he hit her then he walked out and she wants you to go over. Your husband doesn’t want you to go because he needs a lift to the train station in an hour or so because he wants to go out with his mates. You’d seriously tell your sister that your husband comes first so you won’t be going over?
My DH and my sister are equally important to me and when it came to choosing who needed me most and who I would go to would entirely depend on the situation.
If it were a case of my sister telling me she’d seen my DH with another woman but by DH denied it, I would believe my sister over him.
In situations where both of them needed me at the sane time for equally bad reasons I would be very conflicted because I would desperately want to be there for them both. The likelihood though is that I would choose my DH but I would ensure and go out of my way to make sure my sister had someone else with her in my place. To be honest though, my DH would probably tell me to be with my sister because he knows how much she means to me.
Plus - the answers people are giving on here aren’t a true reflection of how things are, or how things should be in terms of loyalty because we all have very, very different relationships with our siblings so our answers aren’t comparable.
Obviously someone who isn’t close to their sibling would pick their DH even if they’d DH’s need isn’t as great, whereas posters who have very close and loving relationships with their siblings will find it much harder to always place them in second position behind their DH/DP.