Family comes first, especially when it’s a once-in-a-lifetime event. It doesn’t matter what else you have planned, you need to make it work, barring some tragedy or just impossible commitment. It’s not one of those things where you can say “Sorry, I have other plans” if you happen to have something on that weekend—you cancel those other plans unless it isn’t possible. Surely, if the girl’s summer camp is three months long, she can be picked up for one weekend to attend her uncle’s wedding.
It’s not clear here whether or not the brother who is getting married actually cares whether or not his niece is there, or if this is something their mother has decided is important. But if the brother wants her there, then this father should be making it work. Usually, it’s more common for someone not to want kids to come to their wedding at all, so the fact that the kids are being asked to come at all really says something.
Whatever the underlying factors here are, the fact that he hasn’t bothered to RSVP for his family yet and his dismissive attitude really make this whole thing seem like he can’t be bothered to make it work for his brother’s event. The fact that he says, ” I kinda assumed our presence is given since we are family,” as his reasoning for not RSVPing, really is the entire point of why his daughter should be going in the first place.
