He didn't have a "relationship" with her, unless you're thinking of the Virtual Reality thing he did, but yes, they knew about him spending time with her.
It is Brian Griffin
Peter Griffin, his wife Lois, sons Stewie and Chris, daughter Megan, dog Brian.
Brian sings Rick Astley's song, "Never Gonna Give You Up"
It is called "Play it again, Brian" and is season 6 episode 10
The main characters in Family Guy are Peter, his wife Lois, children Chris, Meg, and Stewie, and dog Brian. Peter, Stewie, Brian, and Quagmire are all voiced by creator Seth MacFarlane.
When Brian was going to a phsychologist he said " I'm in love with my friends wife Lois"
"Handful of Peter"
Lois.
I think it was when Lois became fat and her and peter had fat sex.
It's kind of complicated. I think he hates Brian because he loves Lois (look who's talking) and like ya know how could he do that to peter who brought him into his home blah blah blah
Pewterschmidt In the Peter, Peter Caviar Eater where they moved in the Cherrywood Mansion the aunt of Lois had the last name of Pewterschmidt.
Nobody currently.He was in love with Lois but that has been resolved and he no longer is.His most serious relationship was with Jillian Wilcox but that has since ended as well.