The issue or case of Lina Medina

Lina Medina is known for being the youngest mother on the Guinness World Records and all global medical records. Lina Medina had her first child aged 5 years, 7 months and 21 days old in 1939. She named her first son Gerardo. Unfortunately, Gerardo died aged 40 in 1979 but the issue or case of Who Gerardo’s father was is still unsolved and the identity of Gerardo’s father is still unknown even though Lina Medina is now almost 90 but still living after getting married aged 38 to another man and produced a second son in 1972 who she still lives with now in Mexico 🇲🇽. How can this case or issue be solved now? Is there a way to find out the father of somebody after their death and if so what is it?