Minimum age to reproduce
The youngest fathers recorded were 11 years old (see wikipedia > 
List of youngest birth fathers).

The youngest mother recorded is L. Medina was 5 years, 7 months and 21 days old when giving birth, which is rather astonishing! Of course, she gave birth by a caesarean section. She had an extremely early puberty; she appears to have had her period when she was 3 years old only. You might want to have a look at wikipedia > List of youngest birth mothers. According to this article, a mother (L. Gryshchenko) became a mother at 6 years old and gave birth "naturally" (not by cesarian section).