Absolutely stand your ground - but try not to get upset. Just let them all know that they have had their special day and now, this time, it's your special day.
I wish I could have had more people/attendants but this isn't our first marriage. There is just 11 of us. I'm divorced and my FI is a widower, however, this is the first "real" wedding that I've had, so we're making it as special as we can. One of my daughters is my MOH and his son is his BM, however, I have another daughter that is pregnant and her doc told her no way she could travel at that time (we thought we were planning it early enough for her to attend). My FI's daughter won't come - she thinks it would be "weird" to see her father get married. I don't think it's anything personal towards me, she just doesn't want her father to be with anyone (she's 28, married with a 4 year old). Just had to vent, myself. Sorry it's on your post. Good luck - and keep your chin up.