Bruce Wayne has many children... Too many, but he likes to collect, I mean, adopt children. You and Thomas are twins, Bruce had them since they were babies, both adopted. His other children didn't know about him adopting two babies while they... Received the best character development (traumas). Now they are surprised to find two identical children in the living room with their father

Bruce: "Oh,guys. I see you're back from your missions and stuff. How are you?"

Dick: "Oh, littles siblings!... Is that good or bad?"

Jason: "more kids? Don't you have enough?"

Tim: "Where did you get those?"