Brothers & Sisters is episode 15 of family guy season 09. It was originally aired on April 17, 2011.
When Mayor West marries Lois’ sister, Carol, they move into the Griffin’s house to be one big “happy” family. To make room for everyone, Stewie is bumped out of his room and takes over Chris’ room, but not everyone is annoyed by the change. Peter and Mayor West bond and become best friends.