I'm going to go ahead and call this one as
bullshit.
The boys dad has 9 kids, and most likely couldn't afford another.
The dad manages to knock some random underage girl up,
and finds himself in a quandry:
"Hmm, I might be charged for pedophilia and have to deal with another kid on top of that. Thinks are not looking so good. I know, I'll just say the knocked up girl and my oldest son are the parents. The DNA match would be so close that no paternity test would be the wiser. Imma get me a beer."
Open and Shut case Ladies and Gentlemen.