Thomas Picard was the son of Jean-Luc Picard and one of his five children with Elise Picard during his Nexus experience in 2371. (TNG movie: Generations)
Jean-Luc thought of Thomas when he again encountered the Nexus in 2384. When he was unwillingly taken into the energy ribbon, one of the illusions that Picard experienced was the now dilapidated home where Elise, their children, and Rene Picard had celebrated Christmas. (TNG eBook: The Stuff of Dreams)