Bartholomew is enigmatic and unpredictable; while he makes an honest living selling inks, and can be very kind and courteous to other vendors, he may have ulterior motives. He has been known to make cryptic messages involving the oceans and their relations with the sands.
Sebastian is a vampire squid (Vampyroteuthis infernalis) that lives in deeper ocean than Bartholomew does. He can only communicate using bioluminecsence, and because of this, Bartholomew twists his words to make botched slogans. As a squid without ink, he has no place in the family business. His relation to Bartholomew is unknown.