Castor isn't an Astral
So we know that Gemini controls duality, and is an entity of duality. The are made of two, one male, one female, one calm, one excited, two opposites but one together. But they are both made of star power.
Castor has mentioned that he gets headaches when people use star power, similar to Lunar getting nauseous in reaction to negative star power. It also seems odd because, from what we can see, Castor, and by extension Gemini, is one of the most disliked among the Zodiac council. Castor is the one assigned to warn people of the consequences of using star power, despite the fact that most of the people who use it have a moral compass that is not unwilling to kill anything in their way. Additionally, Castor has been weirdly insistent that he can die. It is not as though the other Astrals are all immortal, Gemini has mentioned that the Astrals reincarnate when they die, but not only is Castor insistent that he can die, Pollux has also expressed concern for his life. Now this is normal, what with them being siblings and their apparent life-link, but we do find it odd that it has been pointed out multiple times. From what is seen it can be assumed that Castor is at least the weakest of the Astrals. But we think there's something more-
Lunar has mentioned that negative star power makes him feel nauseous but Castor has never mentioned feeling anything about negative energy, but has mentioned that the use of star power gives him a headache. So what would that lead us to?
Castor is a being of negative star power.
It explains why he is generally disliked by the Astrals, being what they are trying to stop. It explains why it is so implied he can die to a mortal being using star power, the method for getting rid of negative energy being to overpower it with positive energy. It explains the poor reaction to star power. AND it makes sense for the concept of duality Gemini represents!
