On one level or another you are allowing what you're family is doing to
you. Families can get pretty vicious at times.
One thing you can do is - if it's your computer you can insert the original
operating system and reboot the disk, and assign your account as the
administrator account and set all other accounts to Parental Controls.
Make sure you back up all of your files before doing this because it will wipe
everything out - including their information. If that's too drastic then
go buy yourself a new computer (they begin at Costco under $400 and you get a
good warranty), make your account the administrator and lock out everyone
else. You're going to have family consequences if you do this so the
choice is yours and it might cost you a wedding. However, if you wish to
stop taking the crap you're currently getting you're the one who is going to
have to stand up for yourself.
Families can truly be vicious - that's why I divorced mine.