A serial father is generally someone who has children with more than two woman.
Desmond Hatchett, a 29 year old who lives in Knoxville, Tennessee, has fathered 21 children with at least 11 different mothers. He was called to court last week where he appeared on the docket eleven times to answer for 15 of his 21 children who haven't received child support recently.
In Russia, Yakov Kirillov, the most productive serial father, had 72 children (57 from the first wife and 15 from the second one). Yakov was a farmer. He lived in the XVIII century. In 1755, at the age of 60, Yakov Kirillov was introduced to the queen for his fartherhood achievements.
PS: Actually his wifes, especially the first one who gave birth to 57 children, are greater heros.