Welp... if we're going to get all technical about "little brother", let's remember that aggy was created as nothing more than one College, of The University of Texas.
It stayed that way for a long time - as realized in their Spirit song, which needed to have its words changed from "... the Aggies are we, we are from Texas AMC" to "... the Aggies so true, we are from Texas AMU" to preserve the rhyme, after they got permission to call themselves a University. They knew.
Hell, Texas College of Mines knew they were more of a brother to aggy, well before becoming UTEP.
So, aggy, the bottom line is that in fact, Texas is not a brother to you at all, not big brother, certainly not little brother.
Texas was, is, and will always be:
YOUR DADDY.
Hook'em.