Don’t like his sister ..

So your wedding isn't for a couple of years, so getting a guest list together isn't really needed yet. You have time to consider things over the upcoming year or two. Generally, I would say invite her, because the drama involving not inviting her will likely be worse. Whether or not you like it, this person will now be in your family. You don't want resentment for the rest of your days about this.

I would invite her, for all the reasons you mentioned.

He needs to make the decision to invite her or not. Unpopular opinion, but if they don’t make any effort to regularly talk or interact in everyday conversations, then there is no relationship and sharing dna doesn’t entitle anyone to an invitation. Chances are you and fiancé may get closer to her over time or neither of you will. Typically with siblings, they already know by adulthood whether they get along with someone or not and it’s not for an outsider to judge that they should “make up their differences because they are family” out of the blue.


Also, unpopular opinion, but the guest list should be loosely visited at this time, because it is one of the first things you need to decide on before you can find a venue for capacity reasons (making sure that the venue is the proper size without over inviting anyone to fill seats). But you don’t need to finalize actual details of specific names until 12 months out when save the dates are sent

There’s no rule that you need to send save the dates to everyone on the guest list so you have even more time than that. Your wedding is not for at least two years. I’d focus on repairing the relationship if possible, not the wedding guest list in the meantime. But I agree with PPs that there’s no coming back from excluding a sibling.

Don’t. you have no reason to. why feed a mouth that doesn’t like you?

I’m on team don’t decide yet, see how it shakes out. You’re very far out still, and the relationship might change (for better or worse) in the next year before you send out invitations.