I truly understand why you are upset about this.Yep ,your brother knows your daughter will graduate this year.But he made his plans with his family.And that is his decision.Others have given you good advises. Let his absence not ruin the joy of your daughter's accomplishment. Enjoy the event.Sometimes relationship with FOO is complicated.My sibling s kid graduated in 2021.I was planning a lot for the event and was in much euphoria for the occasion .I was expecting the invitation with out a doubt as I was close to the kids and babysat them whenever possible.I never got invited.I later knew through my parents that graduation was over.I was really upset and felt used.(my sibling would always tell me how her kids adore me and wanted to spend time with me and would drop them at my place for a week or so)Now I have introspected my entire relationship with them.I was never invited over for any birthdays,anniversaries. They were only missing me when either they are sick or parents have a date night or have a vacation but parents are busy working.None of them have any heart felt connection with me in the same way I do.I was used for their needs.It was not reciprocal and mutual.Ya good idea to lower our expectations.And congratulations to your daughter.