When this man is upset with his sister, he asks Reddit:
My (37m) sister (29f) is getting married in June. I have two daughters one neurotypical (7f) and one high needs nonverbal autistic daughter (5f).
My sister made a rule about her wedding no kids under 5, which I think was a "polite" way of excluding my disabled child. My wife or myself would have immediately took her outside if she had a meltdown.
As my 6 year old nephew (also neurotypical) just "made the cut" and gets to go, there's only two other children under 5 in the family no known disabilities yet. I understand her wedding her choice, but I'm not okay with including one of my daughters but not the other.
Problem is my 7 yr old daughter really wanted to go, she's a real "girly girl" loves pretty dresses, princesses, fairies, and yes brides too. She was excited getting to see her aunt in a bridal gown (the last wedding she went to she was too young to remember).