Alternate timeline(covers information from an alternate timeline)
In an anti-time future, Sidney La Forge was the child of Geordi La Forge and Dr. Leah Brahms. Sidney's siblings were Alandra La Forge and Bret La Forge.
Jean-Luc Picard inquired about Sidney and the child's siblings when he reunited with Geordi around 2395. (TNG: "All Good Things...")
This character was only mentioned in dialogue.