President who had sex with someone not his wife in a White House coat closet confirmed to have love child with said woman

No, not Bill Clinton.

Warren Harding. (A Republican it should be noted)

http://www.nytimes.com/2015/08/13/us/dna-is-said-to-solve-a-mystery-of-warren-hardings-love-life.html?_r=0

Apparently the families of the two trysters care about this. If I were related to Harding in any way, I would probably deny it for other reasons. He is often rated as the worst president (certainly in the bottom three or so).