Ken is probably around 20 years old.
In Mr. Meaty
Ken is Josh's big brother who torments him and Parker with his friend, Darryl. Sometimes, JOsh's Parents plan to send Ken to military school but they won't take him because Ken doesn't want people shaving his hair.
Ken is extremely annoying and heartless. He has a hobby of bullying people, especially Josh and Parker.
However, Ken and Josh seem to be similar in their characteristics.