I'm going to have to go with Riou. "Apparently" a great leader indeed, since the game seems to insist he is when he does nothing that would really inspire confidence.
You win!
1. I have a lot of fans.
There was no one who opposed Riou becoming the leader of the <Whatever> Army.
2. I am also apparently a great leader.
As Snowfire said, he's apparently this amazing leader but never... does anything.
3. I have a famous rival. (No Eph it isn't Dist this time. OR IS IT?)
Jowy. Or Luca. Either or.
Future clues would have been:
4. I have a brother and a sister. Well... not -exactly...
5. It is said I can act as a Shield to protect people.
And... go!