the guy having hundreds of children - was the increased chance his children meet each other and start a relationship and make babies.

That's exactly what I was referring to. Imagine the complications.

I remember I've read somewhere that Pavel Durov has publicly revealed that he has more than 100 biological children across 12 countries. There has to be a limit somewhere in my opinion, if we don't want to wake up half of the population being relative of the other half.

This is what AI gave me:

Yes, it is entirely true. Pavel Durov has publicly revealed that he has more than 100 biological children across 12 countries.
He began his journey as an anonymous sperm donor around 2010, starting out when a friend struggling with fertility issues asked him for help. After that first donation, the clinic clinic manager convinced him to continue donating, citing a severe shortage of "high-quality donor material".
His unusual family structure and personal views on the matter include the following details:

• Official vs. Donor Children: Beyond his 100+ donor offspring, Durov is the "official father" of six children whom he fathered naturally with three different partners.
• Massive Inheritance: Durov stated during interviews with media outlets like Le Point that he intends to leave his estimated $14 billion to $17 billion fortune equally divided among all his biological children—provided they can verify their connection via DNA.
• 30-Year Inheritance Lock: To ensure his kids grow up independently and don't rely purely on trust funds, none of them will be allowed to access their share of the inheritance before the age of 30.
• Active Fertility Campaigning: Durov views sperm donation as a civic duty to fight global infertility. His frozen biomaterial has even been featured in exclusive marketing campaigns at clinics like AltraVita IVF Clinic in Moscow, where he offered to cover the full IVF costs for select women choosing his sperm.
• Open-Source DNA: He has announced plans to eventually open-source his DNA so his biological children can more easily locate and connect with one another.