Isabelle’s twin brother in the Animal Crossing series is Digby.
Digby is a dog, like Isabelle, and both characters were introduced in Animal Crossing: New Leaf. While Isabelle serves as the player’s secretary and assistant, Digby works at the Happy Home Showcase, where players can view model homes and exchange design ideas. His job makes him a natural counterpart to Isabelle’s town-hall role.
The pair are recognizable by their matching Shih Tzu design and related professional roles. Isabelle is usually associated with municipal administration, announcements, and town support; Digby is associated with housing displays and architecture. Their family relationship is explicitly described as twins, not merely siblings or colleagues.
Players sometimes confuse Digby with Lyle, another character connected with homes and property. Lyle is an older insurance salesman who appeared in earlier Animal Crossing games and later worked with the Happy Home Academy. Porter and Harvey are also dogs, but neither is Isabelle’s twin brother.