James Peak died of stab wounds last year, the third violent death in his family.
His brother, too, had been fatally stabbed, his sister shot and killed by a man who mistook her for a thief.
Both their killers are serving lengthy Florida prison sentences. On Thursday, a judge ordered Peak's killer to join them.
As part of a plea agreement, Michael Edmund Smith, 30, pleaded guilty to second-degree murder with a weapon and false imprisonment in exchange for 40 years in prison.
Initially, he faced a first-degree murder charge and a life sentence.
Smith said nothing in court Thursday. He already had confessed to the May 30 attack, telling deputies he stabbed Peak because he thought the Gibsonton man was messing around with his girlfriend.
Peak's sister was Crystal Stith, who was the mother of two of Smith's children. She died at age 19 in 2002, shot in the head with an assault rifle.
Their brother, Joseph Peak, was 17 when a man stabbed him to death in 1994 at Whiskey Stump, a beach surrounded by thick woods south of Gibsonton.
In her 25 years on the job, prosecutor Ada Carmona said she can't remember another family suffering three violent, unrelated losses in so little time.
Colleen Jenkins can be reached at firstname.lastname@example.org or (813) 226-3337.