Castor and Pollux are very similar in a lot of ways. As we point out in the family section, they're practically inseparable. The one major difference between them is that Castor in mortal and Pollux is immortal. Castor is the son of Leda's mortal husband, Tyndareus, while Pollux is the son of Zeus. Amazingly, this difference never seems to cause any tension between the brothers. You'd think Castor would get jealous or something, but nope. In fact, Pollux's immortality leads to a beautiful moment of selfless sacrifice after Castor is mortally wounded. Instead of letting Castor go down into the Underwold, Pollux begs Zeus to let them share his immortality. This selfless act leads to both brothers being given a place in the stars. In a way, the thing that made them different, in the end brings them together forever.
Questions About Mortality
Does Castor deserve the mortal wound he receives from Idas? Why, or why not?
Why do you think Castor never seems to be jealous of Pollux's immortality?
How would this story be different if both brothers were immortal?