Do Lois and Peter Know Stewie Talks?

According to Seth MacFarlane, himself, everyone IS able to understand Stewie full well. However, characters such as Peter and Lois just choose to ignore him the way most people do with children, believing in the idealism that “Children should be seen and not heard.”

Can Lois hear Stewie talk?

MacFarlane went on to say that Brian always hears Stewie, and more recently so does Chris, but the writers usually strive for Peter, Lois, and Meg not to hear him.

Is Stewie in love with Brian?

While I do believe Stewie is probably gay or bi, I don't think he has a crush on Brian. Rather, Brian is just an uncle or second father to him, but because Stewie is a baby growing up in a dysfunctional household, he thinks it's romantic love, not paternal love.