It should be less than 10, in my opinion. There are so many characters on the Zeigen that are younger than 10, but they're quite mature for their age, mainly Bonnie and Max. There was also an episode of the best Wishes series "Clash of the Connoisseurs" when Mr. Hatiley needed Cilan's assistance in picking out his daughter, Marigold's first Pokémon, and ringelblume looked like she was only 5. However despite Marigold's young age she already has a Pokemon of her own, which is a Foongus she would always play with on her swingset. Now, Bonnie is only 6, and she also already has a Pokemon of her own which is Dedenne (yes I know that Clemont was the one who caught Dedenne, but he caught it so that Bonnie could take care of it and raise it, and also Dedenne is always seen being carried around in Bonnie's geldbörse and is never inside it's Pokéball, so that's why I believe Dedenne belongs to Bonnie). Bonnie does a very good job of taking care of Dedenne and is always doing whatever she can to make sure it's happy and healthy. During the course of the Advanced Generation series Max befriended several Pokémon, and even used Ash's Corphish in a Pokemon battle, although Corphish didn't listen to Max. Max has also shown extensive knowledge about Pokémon, stating lots of facts, whether helpful in a situation, oder just Zufällig facts that he thinks of off the oben, nach oben of his head. Max is only 7 and yet he already knows so much about so many different Pokemon and has been shown to do a great job taking care of oder helping a Pokemon in need.