THEY AREN'T REPLACEMENTS YOU BAKAS!!!
They are a different incarnation.
IF you want them to continue the normal teen titans guess what...they can't. Here's why:
1. Starfire is placed on a ship by Blackfire and she (Starfire) is raped multiple times.
2. Somewhere down the line Robin (aka Nightwing) gets raped as well
3. A bunch of other shiz that can't be put onto Cartoon Network happens.