Invitations hell

So, we chose a date based special to me as I lost my dog (he was basically my first "child") on that date last year. It turns out to be the same day as my partner's sister-in-law's birthday. It wasn't in our minds that it was her birthday as that date simply became an anniversary date. She initially said she couldn't come because it was her birthday which meant that precluded my partner's brother and two nephews from attending. When we met a few days later she said (presumably feeling guilty) that they would work something out. Then the following day my partner got a call from his brother to say they couldn't come. We haven't even sent invitations yet, simply asked people to save the date.


My future mother-in-law was upset and told them so. They now want to come and are expecting an invitation. I don't want them there because of they way they have reacted - her birthday wasn't even in my mind when I chose the date so it was in no way on purpose but we have been made to feel guilty about it. Is it reasonable not to want them there? My partner says he doesn't want them there but it is his brother so that would be hard for him I do feel that they didn't consider his feelings at all and that my sister-in-law could still celebrate her birthday without throwing the tantrum she did. Do I have to invite them?