Not me, but years ago my sister ended up in the ER on Christmas Day & she missed my first wedding because she was in the hospital also due to bleeds.

Yes, holiday events have been affected. Have spent a number of holidays or birthday events in the ER.

No, why should your condition mess up others holiday plans.
Do an assesment of the environment and your mobility and adapt if need be.
Otherwise the family must carry on and do what they want, and you occupy yourself with something else

A lot of times! This coming Thanksgiving for example

Rarely....