"Shit" is used in a few episodes.
Fuck is used only twice in the entire show. One time, Pete says 'Oh Fuck!' in front of his children. And in the intro to an episode Jake says "you fucking idiot!" To Ben.
B-tch is said in many episodes.
A little girl (about 7) is seen sitting on the stairs telling Karen's parents that her (the little girl's) mum "said the F-word and the K-word".
One episode contains arguing between the mum and her sister, and they're swearing a lot, but then Karen comes down to them (she's about 5-6 in that episode) and says: "What are you doing?" then the mom replies: "Um, we're in a game, the one to shout the stupidest thing wins. Wanna join us?" And Karen says "No thanks." Then they continue arguing.