As reported by US media.

They must have multiple children via wives/surrogates/etc such that there is a time interval of 3 years such that there are at least 50 children born within it. The person of interest can be the father or mother, as long as the children are substantially their genetic children (some minor genetic modification may be allowed)

e.g. this story, where through surrogates, they have a huge number of children with birthdays just a few months apart: - children ages: Mustafa, 19 months; Mariam, 18 months; Ayrin, 18 months; Alisa, 18 months; Hasan, 17 months; Judi, 17 months; Harper, 16 months; Teresa, 16 months; Huseyin, 16 months and Anna, 15 months.

https://www.dailymail.co.uk/femail/article-10934703/Russian-woman-21-babies-Turkish-millionaire-devastated-arrest.html

Woman who has 21 babies with millionaire is devastated by his arrest

Kristina Ozturk, 24, who lives in Batumi, Georgia, has 21 surroagte children with Galip Ozturk, 57, who owns the bus company Metro Turizm. He had already fled a murder sentence in Turkey.