Though he's El Patrón's grandson, El Viejo actually appears to be a lot older than El Patrón. That's because El Viejo opted to age naturally, which is seen by his grandfather as beyond foolish. El Patrón tries to convince El Viejo to use a clone and get some organ-upgrades, but El Viejo refuses. He's very religious, so cloning himself would go against his beliefs. When his son, Mr. Alacrán, tells El Viejo that he'll surely die without chemotherapy to treat his cancer, he merely replies, "God wants me to come." (9.29) We definitely give him some props for standing by his convictions. That's hard doing in Opium.
When El Viejo finally dies, Celia says that the family has lost it last decent member, and we're left to wonder: how did El Viejo hold onto his beliefs and stand up to his powerful grandfather? Where did he get those beliefs from in the first place? We're guessing his mother and perhaps his own father, the long-dead Felipe, may have had something to do with it.