Janet and Robert are a husband and wife whom Stewie knows and attends the wedding of in "Snap(ple) Decision". Supposedly, the two almost called off their marriage due to an unspecified incident in Jamaica, but Janet forgave Robert for it, prompting Stewie to deem her spineless.
While at the wedding, Stewie is stunned when Brian also shows up, considering the recent end to their friendship. The two spend the evening avoiding and smack-talking each other until they cannot take it anymore and reconcile, culminating in Brian performing "Stewie, Stewie" as an ode to their bond.