Plutarch, The Life of Cato the Younger 3

He was so celebrated that, when Sulla was preparing for exhibition the sacred equestrian game for boys​ which is called "Troja," and, after assembling the boys of good birth, appointed two leaders for them, the boys accepted one of them for his mother's sake (he was a son of Metella, Sulla's wife), but would not tolerate the other (who was a nephew of Pompey, named Sextus), and refused to rehearse under him or obey him; and when Sulla asked them whom they would have, they all cried "Cato," and Sextus himself gave way and yielded the honor to a confessed superior.

Now, Sulla was friendly to Cato and his brother​ on their father's account, and sometimes actually asked them to see him and conversed with them, a kindness which he showed to very few, by reason of the weight and majesty of his authority and power. 

So Sarpedon, thinking that this conduced greatly to the honor and safety of his charge, was continually bringing Cato to wait upon Sulla at his house, which, at that time, looked exactly like an Inferno, owing to the multitude of those who were brought thither and put to torture. 

Now, Cato was in his fourteenth year; and when he saw heads of men reputed to be eminent carried forth, and heard the smothered groans of the bystanders, he asked his tutor why no one slew this man. 

"Because, my child," said the tutor, "men fear him more than they hate him." 

"Why, then," said Cato, "did you not give me a sword, that I might slay him and set my country free from slavery?" 

When Sarpedon heard this speech, and saw also the look on the boy's face, which was full of rage and fury, he was so frightened that in future he kept him under close watch and ward, lest he should venture on some rash deed.

When he was still a little boy, and was asked whom he loved most, he answered, "My brother"; and to the question whom he loved next, likewise, "My brother"; and so a third time, until, after many such answers from him, his questioner desisted. 

And when he came to maturity, he maintained all the more firmly this affection for his brother. Indeed, when he was twenty years old, without Caepio he would not take supper, or make a journey, or go out into the forum. 

But when his brother used perfume, Cato would decline it; and in his habits generally he was severe and strict. 

At any rate, when Caepio was admired and praised for his discretion and moderation, he would admit that he had those qualities when tested by reference to most men; "But when," he would say, "I compare my life with that of Cato, I seem to myself no better than Sippius,"—mentioning one of those who were celebrated for luxury and effeminacy.