Multiple realities(covers information from several alternate timelines)
John Nesterowicz was a Starfleet officer in the 24th century.
As a captain, he was listed as a Starfleet Academy officer on the dedication plaque of the USS Brattain. (TNG: "Night Terrors", dedication plaque)
In 2353, he was listed as a Starfleet Operational Support Services officer on a directory placard in Starbase 32, Maxia sector. His office was located in room #75274. (TNG: "Violations", directory)
In an unknown, alternate future timeframe, he was listed as a Tactical Systems officer on the dedication plaque of the USS Pasteur. (TNG: "All Good Things..." dedication plaque)
This character was only mentioned in writing.