Gillion was born just outside the capital of the Undersea. The only two family members he has mentioned by name so far are his older sister Edyn Tidestrider and his grandfather Finn Tidestrider. In Episode 50: The Block, though, he asks Oliver if he would come back from the C-Mart unlike his parents after dropping him off for training, though the topic is quickly brushed off. Gillion has seldom, if ever, brought up his parents otherwise, suggesting a distant relationship with them.