How can I get other trainers to LV up their Pokemon in Diamond/Pearl?

Question

I like to train on some trainers near the Survival Area. But for my brother, the trainers have LV60 + Pokemon, and the same trainers have about LV50 Pokemon for me. How is it that for him they are higher LV's? And how do I get them to get higher LV Pokemon?

Answer 1

you have to fight the pokemon in the grass they are weaker then the train and when you get them  about the same level then u fight them.

Answer 2

fight trainers more and they will elvel up eventualy