Re William didn’t stay over with Harry the night before his wedding and caused a fuss about having to go to the hotel he was in the night before for dinner. As his only brother and as best man he should’ve been there with him. We hear all the time how wonderful and amazing Catherine’s family are - surely on the occasion of his only sibling getting married her parents could’ve come over to help her with her newborn and the children for the night. They have nannies and cleaners and staff so not exactly short of help in general.
my DH has only one brother too. He got married when my baby was 6 weeks old post a difficult c-section. We went to the hotel for 3 nights - so DH could have drinks with his brother and bridal party the night before, the night of the wedding and the night after the wedding. I was fine with this as it was his only siblings wedding. Yes it was difficult for me and exhausting but it was important to us both that we made a big effort for his DBro especially as (like Harry) they were missing a parent at the wedding.
from my view either William or Catherine or both didn’t care enough to put themselves out for Harry and his wedding which reflects poorly on them.