How is American Dad a spin off of Family Guy?

I understand how the Cleveland Show is a spin off of Family Guy since
Cleveland actually was a main character in Family Guy but how is
American Dad a spin off? Seems to me that American Dad is simply just
another show created by the creator of both the Cleveland Show and
Family Guy.
I was reading other questions about family guy and the cleveland show
and people seem to think American Dad is also a spin off.