there's literally zero evidence that video games cause violent behavior. What has been noted is that kids with aggressive or violent tendencies can have bad behaviors triggered by video games. However, those same kids can also be triggered by literally any sort of stress, like a game of chess or monopoly.
as for limiting video game time, that's a tough call. My parents severely limited my time. When i got older and they couldn't control it, i went overboard and spent wayyyyyy too much time with them. You gotta find the right balance. Let them play games but also get them outside and active with something like little league baseball.