You have to go through a special gate (it is a door at the Utah Thicket office if I remember correctly... a tent at BYU) and depending on the day/game they are strict about that policy
Your BYU colors better be hidden 🙂
It would be a bad look for your cousin's sons to have somebody show up in the wrong colors. (You are going to get a lanyard pass that may have those kids names on it)