As our old readers know, Carlos Merriwell was Frank's deadly enemy, although they were blood cousins.
Carlos was the son of Asher Merriwell, the brother of Frank's father.
At the time of his death, Asher Merriwell was supposed to be a crusty old bachelor, a man who had never cared for women and had never married. But he had not been a woman-hater all his life, and there was a romance in his career.
Asher Merriwell had been snared by the wiles of an adventuress, and he had married her. By this woman he had a son, but the marriage had been kept a secret, so that when she deceived him and they quarreled they were able to separate and live apart without the fact becoming public that Merriwell had been married.
Fortunately the woman died without openly proclaiming herself as the wife of Asher Merriwell. In her veins there had been Spanish blood, and her son was named Carlos.
After the death of his wife, Asher Merriwell set about providing for and educating the boy, although Carlos continued to bear his mother's maiden name of Durcal.
As Carlos grew up he developed into a wild and reckless young blade, making no amount of trouble and worry for his father.
Asher Merriwell did his best for the boy, but there was bad blood in the lad's veins, and it cost the man no small sums to settle for the various "sports" in which Carlos participated.
Finally Carlos took a fancy to strike out and see the world for himself, and he disappeared without telling whither he was going.
After this, he troubled his father at intervals until he committed a crime in a foreign country, where he was tried, convicted, and imprisoned for a long term of years.