Hey girl!
You're definitely not alone!!
My situation is reversed...my FI's parents will not be there....his father told us at Christmas that him and his wife won't be coming to the wedding because they already spent their $$ on a trip to Europe. (WHATEVER) and now his mom isn't coming. It's less than 2 months away and she hasn't booked yet (even though when we first told her our wedding plans, she PROMISED she would be there no matter what!) and has been dropping hints about not being there.
My father passed away 7 years ago as well...I feel your pain about having no one to walk you down the isle...it'll be a sad day for me!
About your comment when you said your bother mentioned you were being selfish-you are definitely NOT being selfish! This is YOUR and your FI's day, not your family's. No matter where you have your wedding, or what day, or what time of year-someone will always find a reason to complain or voice an opinion. As hard as it can be sometimes, just remember you're doing this to make you and your FI happy, not everyone else!!
Hang in there!!!