Sorry, but there is only one TRUE Answer:
Tim and Conner..
It was PERFECT in the actual Young Justice Series when the evil scientist of STAR Labs said that Conner left and said that his friends are annoying.
Tim spoke with the others and said that he (Tim) LOVES Conner and if Conner would have wanted to stay in Gemworld Conner would have spoken with him and Tim would have been happy for him, because what makes Conner happy, makes him happy...
Or all the cloning attempts
Or how he changed his costume and I loved how Tim after Conners death told the others the story when TIM and CONNER went to Toyman (Hiro) Place and were looking for him.
It was so funny (Conner had fun with female robots while Tim nearly died)...