The largest gathering of people with the same first and last name occurred in Tokyo on 29 October 2022. Present were 178 people called Hirokazu Tanaka. https://www.guinnessworldrecords.com/world-records/largest-same-first-and-last-name-gathering
According to the Japan Times, the previous record was set in 2005 by American business person Martha Stewart and 163 other people of that name.
The Japan Times also explained that the organiser of the gathering was the Tanaka Hirokazu association. The founder—of course, Hirokazu Tanaka—said it was the group’s third try. Failed attempts gathered 71 Hirokazu Tanakas in 2011 and 87 in 2017.
The earlier attempts failed because the association gathered only people spelling their names with the same Chinese characters (Kanji). But because the guidelines for the record recognise any names pronounced the same, the association called this time for Hirokazu Tanakas who spell their names using any Kanji. https://www.japantimes.co.jp/news/2022/10/29/national/guiness-record-hirokazu-tanaka/
I remember when 2 professional footballers in the top division of English football were called Gary Stevens—not to mention a 3rd called Trevor Steven. Indeed, all 3 were in the England national squad for the 1986 World Cup. English football fans have long serenaded their favourites with the song ‘there’s only one [name of player]’, sung to the tune of Guantanamera. Needless to say, the fans soon delighted in ‘there’s only 2 Gary Stevens’.