My 8 years old cousin had seizures and fever. he was playing video games for long time. can these cause seizures?

Possible: It is not too common but if someone has a seizure disorder it could provoke it depending on the graphics of the game. Fevers triggered by fevers are much more common BUT usually start around 6 months and end around 6. The fever is triggered by the sudden rise in temp associated with an infection. Having a first febrile seizure at 8 is unusual and a full workup is needed.