Betlehem was born 4 September 2003 in Szombathely, Hungary, and trains with coach László Szokolai as part of the Balaton Úszó Klub swim club.

[2] Betlehem started his competition at the 2020 European Aquatics Championships, held in Budapest, Hungary, with the 5 kilometre open water swim on 12 May 2021, placing twelfth with a time of 56:00.4.

[4] For his third and final event, the 1500 metre freestyle held as part of pool swimming competition, he swam a time of 15:18.18 in the preliminaries on 18 May, placing twelfth overall.

[5] Two months later, at the 2021 European Junior Swimming Championships, held at Stadio Olimpico del Nuoto in Rome, Italy, Betlehem won the bronze medal in the 1500 metre freestyle with a personal best time of 15:02.28.

[9] The following month, as part of the first ever FINA 4×1500 metre mixed gender open water team relay event, contested at the Abu Dhabi Aquatics Festival in Abu Dhabi, United Arab Emirates for the last leg of the 2021 Marathon Swim World Series, he swam the third leg of the relay to help win the silver medal in a final time of 1:06:51.7.

[14] For his final event, on 29 June, Betlehem persisted to be the only male swimmer representing Hungary to cross the finish line in the 10 kilometre open water swim, after teammate Kristóf Rasovszky was kicked in the stomach and had to withdraw from competition halfway through the race for medical reasons, placing fifth in a time of 1 hour, 51 minutes and 29.8 seconds.

[41] The fourth and final day, he won the national title in the 800 metre freestyle with a personal best, 2023 World Championships, and 2024 Olympic qualifying time of 7:49.59, finishing 4.08 seconds ahead of silver medalist Kristóf Rasovszky.