Is it ok for a 13 or 14 year old to watch "Family Guy" on TV at night?

I was observing the show, and it seems it is filled with a lot of adult theme kind of situations...like sex, getting laid, and a bunch of other heavy topics too much for a kid...how can the kid know what they are talking about...am I just naive? THis show seems to appear ok because it is a cartoon...but it is loaded with heavy adult topics....Does the kid's mother know what he's watching?