"Only twins could wreak so much havoc." he knows. They both know. If a god of mischief exists, of course he has a twin!

"Why are twins drawn to us, brother? Or why are we drawn to them?" he closes his eyes as the wind catches his hair, "See? How did I know he would be fond of you?"

Twins and Fëanorians go together naturally. It is best not to question it!