Imagine you are the first born son of your state and at age 7 mom and dad have another son. You did your best to be a good kid but the baby is the apple of your parent’s eye. Your younger brother gets the best room in the house while you are stuck in a tiny room with no AC / heat. At Christmas baby brother get twice as many gifts and all your other relative states know about him but your folks hardly talk about you.
When you grow up baby brother is supper successful with a great job in an exciting new field while you stay in the same town and farm. As you watch your brother ascend to new levels of success you grow bitter and develop an inferiority complex. You bitterly complain to your buddies how you were first and all the success your brother has should have been yours. As the resentment grows you consume yourself with trying to prove that you are better than your younger brother, it’s all you think about.
Your brother comes to town and asks if you want to play a game. Now, you may not have the nice house or the pretty wife but by god you are going to beat your brother at something if it’s the last thing you do. Your brother is annoyed that you are trying so hard, this was supposed to be fun, but if it’s a game you want then it’s a game you’re gonna get. Younger brother wins most of the time but the times you win you feel justified in all your bitterness and the cycle continues. That’s the A&M & Texas rivalry.
It’s a thing because we share a state and the existence of the University of Texas is viewed as an affront to the cult like Aggies. If the Ags cared at the same level as Texas it would be no different than playing Tech, Baylor or SMU. Tex vs OU is equal hate / respect. Tex vs A&M is one side hating and the other side disrespecting.