Age: As old as the hero.
Infomation: He is a friendly player, who just wanders into the region. He is Professor Elm's son, you know, from Johto? He finds you in the 2nd city and says "Hey, do you know Professor Elm? Has he taught you anything? I'm his son, and I was wondering if you want to battle. You do? OK then, bring it on!" And battles you with his Horsea.
In game plot: Can he be your rival? Or at least one of the rivals. He just runs into you after every 2 badges you get (kind of like Carlos in Shiny Gold". Whenever you challenge him, he gets MAD and runs off. He is always like a gym behind you or 2. As I said before, you meet him in the 2nd city (if that's OK) and chalenges him to a battle. And after the battle he is on his way. You battle with him once (like steven in Emerald). Like khaosknight's character, the last time you battle him he is on victory road.
Pokemon:
1: Horsea
2nd time
1: Horsea
2: Larvitar
3rd Time
1: Horsea
2: Pupitar
3: NidoranMALE
4: Chansey
4th Time
1: Seadra
2: Pupitar
3: Nidorino
4: Blissey
5th Time:
1: Seadra
2: Nidorino
3: Pupitar
4: Shuppet
5: Seel
6th Time:
1: Seadra
2: Seel
3: Tyranitar
4: Nidoking
5: Mightyena
7th Time:
1: Kingdra
2: Seel
3: Shuppet
4: Tyranitar
5: Nidoking
6: Houndour
7th Time:
1: Kindra
2: Dewgong
3: Bannete
4: Tyranitar
5: Nidoking
6: Houndoom
Take out whatever ones you want, I don't need all of them...
Feel free to change this to fit the storyline, i just kinda winged it :D