They broke up because she wanted to travel and try new things and he didn't want to go with her. She saw that as a lack of commitment to her.

Oh and with the wedding invite thing, we've only lived together 3 months now, and the invite/RSVP for the wedding happened mid-last year (they planned very early) before we were even together. At one stage we did discuss the possibility of her asking the couple to add a +1 but ultimately decided not to because I'd also need to get out of work, and pay for the additional flight etc. If I had known the ex was going to become such a problem I would've actually pushed to get an invite. Just didn't know it was going to be an issue.