The family background of Chegwidden himself has never been revealed. At age 24, he married Marcella, the daughter of the Mayor of Naples, Italy. In 1972 their daughter, Francesca, was born. Sometime in the 1970s, they divorced and his ex-wife received custody of Francesca. Marcella remarried, to an Italian man named Vittorio Parreti, who was later murdered. Chegwidden has said that although he is proud of his daughter, he wishes that he would have spent more time with her. Francesca ran into problems when she fell in love with mafia member Luciano Antinori.
He has had other romances throughout the years (with judge Laura Delaney and Dr. Sydney Walden) but nothing really came from them. Judge Delaney was killed after stepping on a landmine. His last and longer romance in the series was with Meredith Cavanaugh. They met when she went to JAG headquarters to meet with Mac, but he thought she was another attempt at matchmaking from his subordinates. He later learned that Mac wanted to speak with her about a course she wanted her little sister Chloe to attend and he apologized. They bonded over their common interest for Shakespeare. Although the Admiral and Meredith got engaged near the end of Season 8, he found out she was cheating on him in Season 9 and ended their engagement on the spot.
Lt. Budrick "Bud" Roberts, Jr. (Patrick Labyorteaux) and his wife Harriet Sims (Karri Turner) named their first son A.J. after him, although A.J. is just for the letters, not for Albert Jethro, as Chegwidden originally believed. During episodes where he is stuck at home, he is often kept company by a German Shepherd named "Dammit", whom he encountered when he was accidentally ejected from an F-14 piloted by Harm into a blizzard-covered forest in Virginia.
Chegwidden was a talented pitcher on his High School baseball team. The Cleveland Indians drafted him, but instead he chose to accept an appointment to the United States Naval Academy. After graduating from the Academy he went on to become a Navy SEAL, serving with valor and distinction in the Vietnam War. When the war had ended he transferred to surface warfare, serving aboard destroyers. Chegwidden rose to command an Arleigh Burke-class destroyer; a cased model of one graces the mantel of his office fireplace. During the 1980s, his career took yet another turn as he left Surface Warfare and went to Law School. As a member of the Navy's JAG Corps he rose quickly through the ranks, serving as the head of JAG in the Pacific before being appointed Judge Advocate General of the United States Navy in 1996.
Many years later, as private lawyer, Chegwidden was asked to represent Senior Special Agent Leroy Jethro Gibbs.
He is a member of the Bar Associations of Virginia, Maryland and New York.
Chegwidden often comes across as being hard-nosed and very bound to his position. However, he has been known to show vulnerable moments in his life and career, and is fiercely protective of those he considers to be "his people."
When Bud was wounded after stepping on a landmine, Chegwidden attempted to soothe the news to Harriet and seemed to be a little melodramatic while doing it. Another time he showed his softer side was when he broke the news of Harm's aircraft accident while attempting to return home in time for Mac's engagement party to Mic Brumby (Trevor Goddard).
He also is known for playing the absent father figure to several of the JAG staff. When Bud and Harriet lost a stillborn child, the Admiral attempted to help both by granting an emergency leave.
Chegwidden is also known for showing a side of himself that frightens most who have seen it. The "Old Man" may be the Navy's Judge Advocate general, but he has never forgotten his roots as a Navy SEAL.
In one episode, he broke the nose of Special Agent Clayton "Clay" Webb (Steven Culp) for putting Harm and Mac in danger. This particular incident impressed Webb so much that he never again tried to ruffle the Admiral's feathers.
He was responsible for the death of Antinori after Antinori had kidnapped Francesca. Even though it was Francesca who pulled the trigger, the Admiral was present and made no move to stop her. He had earlier killed several of Antinori's bodyguards.
He also scared Harm on several occasions, most notably when Harm and Mic were responsible for accidentally breaking Bud's jaw. He yelled at both of them, threatening to horsewhip Harm, until he decided on a non-judicial punishment that fit the crime. He ordered Harm and Mic to confine themselves to a warehouse and did not allow them to come out until each had inflicted the same amount of punishment on the other as they had inflicted on Bud.
He even rattled a CIA "sweeper," when he realized that the rogue agent was playing mind games with him. These mind games resulted in the death of the woman he loved.
The Admiral was targeted by the father of a sailor that the Admiral put away, who later was exonerated. Unfortunately, the young sailor had died in prison. Chegwidden had to show considerable restraint to keep from killing the man.
On more than one occasion Chegwidden put his career on the line to back his staff or to help them when they needed it. Perhaps the best example of this was when as one of his final acts as the Judge Advocate General, he went to the Secretary of the Navy and demanded that Bud Roberts be promoted. Roberts had been passed over for promotion because he was no longer qualified for sea duty. The usual result of being passed over is involuntary separation from the Navy. Chegwidden argued that passing over an officer due to a wound received in the line of duty was immoral. Bud's promotion to Lieutenant Commander was duly made as Chegwidden's final official act as the JAG.
It was mentioned that he became a senior lawyer at some private firm around the Washington DC area. In the NCIS episode Damned if You Do, he appeared as a civilian attorney to represent Agent Gibbs when the latter was charged.