When Megumi was very young, his name was Zen'in Megumi, though that name did not last long. Following the "death" of Megumi's biological mother, Toji found another wife and married into her family, and Megumi officially changed his name to Fushiguro Megumi.
Of course, this marriage was actually in name only. Toji and Ms. Fushiguro had a prenuptial agreement, and the marriage was purely a formality.
Back when he was still Zen'in Megumi, Toji fell into a deep slump for a period right after her "death," failing to properly care for tiny little Megumi. Fortunately, the boy had a tenacious vitality and managed not to starve to death.
Chapter 316