De Sousa was born in Luanda, Angola to Jean Conceição and Janina De Sousa and has three younger sisters: Aline, Luisa, and Alicia. In his childhood, he played soccer and basketball, but he decided to focus on the latter sport at age 10.
High school career
Shortly before his freshman year of high school, De Sousa moved to the United States. He first attended Montverde Academy in Montverde, Florida. Under head coach Kevin Boyle, he helped the team remain ranked top-5 in the country and was considered its best prospect. After having to share playing time with top prospects and forwardsSimisola Shittu and E. J. Montgomery, he chose to leave the program after his sophomore season. For his junior year, De Sousa transferred to IMG Academy in Bradenton, Florida, as decided by his parents. Although IMG also had touted big men, Isaiah Stokes and Emmitt Williams, his decision ultimately gave him more playing time than at Montverde. In the summer of 2016, he also competed with the Under Armour Association team Florida Vipers, averaging 20.5 points and 8.2 rebounds per game. In August of his senior year, De Sousa committed to Kansas and reclassified from the recruiting class of 2018 to 2017 while exploring the chance to graduate early from IMG Academy and join the Jayhawks in time for the second semester of the 2017–18 NCAA season. He successfully completed his academic requirements at IMG Academy and graduated early, in December 2017.
During the October 2018college basketball corruption trial of two Adidas officials and an aspiring NBA agent, testimony was given by TJ Gassnola, a former consultant for Adidas, alleged that De Sousa's guardian, Fenny Falmagne, had accepted $60,000 from an unnamed Maryland booster to steer De Sousa to that program. Gassnola further testified that he gave $2,500 to Falmagne to cover the cost of online courses that De Sousa needed to graduate high school early. He also agreed to pay $20,000 to Falmagne to help release De Sousa from the commitment to the Maryland booster, but that the proposed payment was never made. De Sousa ultimately committed to Kansas, one of the named victims in the federal indictment. Falmagne has vehemently asserted that neither he nor De Sousa accepted any money to steer De Sousa to Kansas, stating that "Coach Self is not about that. That is one of the things I really appreciate about him.... That's when we went over there." With De Sousa's amateur status now in question, on 24 October 2018 Kansas announced that De Sousa would be held out of competition until an eligibility review was completed. On 1 February 2019, the NCAA ruled him ineligible for the remainder of the 2018–19 season and all of the 2019–20 season. Kansas Athletic Director Jeff Long immediately announced that they will appeal. Head coach Bill Self called the entire process and decision "mean spirited" and "vindictive". On 18 April 2019, Kansas officially filed the appeal with the NCAA on De Sousa's behalf. The following day, he declared for the 2019 NBA Draft but also announced he planned to return to Kansas if he won his appeal. On 24 May 2019, the NCAA announced that he had won his appeal and will be eligible to play in the 2019–20 season. The following day, he officially withdrew from the draft.
Junior year
On 21 January 2020, in a game against Kansas State, De Sousa was dribbling out the ball in an 81–59 game in favor of Kansas when he was stripped by Kansas State player DaJuan Gordon with 3.1 seconds remaining in the game. De Sousa blocked Gordon's dunk attempt as time expired then stood over and taunted him, which sparked a brawl between both teams. De Sousa threw several punches and picked up a chair before he was restrained by assistant coach Jerrance Howard. De Sousa was suspended indefinitely by Kansas for his role in the brawl. The Big 12 announced his suspension will be 12 games, however, Bill Self stated he may continue the suspension beyond the 12 games. He was eligible to return for the Jayhawks’ final regular-season game against Texas Tech on 7 March.
