The both sons of the current ones so why not let them take the spotlight together.

Superboy...no...nothing like superman,(dont even think he should exist)

damian..yes....just like batman

of course he should exist,he is the result when humans try to recreate god(or superman),but instead get something different,in someways good,and in many ways bad. 
 
saying he shouldnt exist is silly,thats like me saying kara shluldnt exist,and kal should have been the only survivor from krypton,and of course i wouldnt say that,kara is cool too.