Victor Atreides was the first son of Duke Leto Atreides I, and half brother to Paul Atreides. His mother was Kailea Vernius, sister to Rhombur Vernius of Ix, and he was conceived and born on Caladan after the loss of status of House Vernius.
Leto and Kailea
Leto had desired Kailea all during his teen years, especially after the exile of Rhombur and his sister to Caladan, after the Tleilaxu takeover of Ix. For years, Kailea lived with Leto in Castle Caladan, and was a constant friend and companion to the growing ducal heir. When Leto's father, Duke Paulus Atreides was gorged on the horns of a Salusan bull, Leto was forced to exile his mother, Helena Atreides, to the Eastern Continent of Caladan, for her secret role in her husband's assasination. During all of these turmoils, including Leto's ordeal at his Trial by Forfeiture, Kailea was there to comfort and help him. Soon afterwards, Kailea and Leto became intimate, Victor was conceived, and born in Cala City.
Victor's childhood was a happy one, even though realtions between Leto and Kailea grew strained over time, especially after Kailea obtained a Lady-In-Waiting from the Imperial Court on Kaitain, Chiara, who was actually a spy planted by House Harkonnen. Over a long period of time, the servant ever so slightly planted false info and manipulated Kailea to turn against Duke Leto, and Victor witnessed many arguments between his mother and father.
Death on Caladan
Soon, Kailea and Chiara plotted to assassinate Leto, and have Victor assume the ducal rights of House Atreides. Kailea began to set the plot in motion and seduced Atreides House Guard Captain Swain Goire. After a tryst with the Guard Captain, Kailea stole his keycard to the Atreides armory, and gave it to Chiara. Chiara ransacked explosives from the Armory, and placed them on the skyclipper air vessel that Leto planned to navigate to visit various points of interest on the Western Continent. On the day of the procession; Victor begged Leto to accompany his father on the week-long journey, which Rhombur later joined, as well. As the three of them lofted gracefully over the settlements north of Cala City, Victor discovered the explosives, and accidentally triggered them. Victor was killed instantly, and Leto and Rhombur were severly wounded.
Kailea learned of her son's death, and deeply stabbed Chiara with Goire's ceremonial blade, and then threw herself from a tower window in Castle Caladan. Goire went to Thufir Hawat and threw himself upon the mercy of the Duke. Leto sentenced Goire to live and never forget the pain he caused, and that he would never regain his Duke's trust; and exiled him to live with his mother on the Eastern Continent. Goire's reply was "someday they will call you 'Leto the Just.'
Shortly thereafter, Prince Rhombur received cyborg implants from Dr. Wellington Yueh, and lived on. Leto was awash in grief for his son, but refused to accept a ghola of Victor from the Tleilaxu, as he considered their takeover of Ix unjust. Leto did, however, recover enough to lead House Atreides again.
It was the deep grief that Jessica saw over Victor's death that caused her to conceive a "replacement" son for Leto. Even though she knew this would set herself against the wishes of the Bene Gesserit, and their complex Breeding Program, the joy she knew Duke Leto would feel, convinced her to conceive Paul Atreides after this incident.