In Family Guy S10E22 "Family Guy Viewer Mail #2", Brian says that Family Guy is based on an English show named "Chap of the Manor".
Ιs there actually a show that resembles that?
Wikipedia doesn't have any insight.
That Wiki link actually has a lot of insight. The first line in the plot section:
Premise being the key word.
In the Cultural References section:
The reference to The Simpsons should give you an indication that the tongue is firmly planted in cheek.
Too many obvious references to other famous British shows.
Putting all of this information together, it's pretty obvious that Chap Of The Manor is fictional.