"Childlessness is hereditary in our family" What do you call a statement containing a contradiction such as the example?

This kind of sentence is usually absurd and may or may not be recognized as such by the person who utters it.

She will regret it till the day she dies, if she lives that long!
"Aren't you going to John's funeral? After all, you were best friends." "Why should I? I'm sure he won't come to mine."

Solution 1:

The actual term is Irish Bull. (Credit to Centaurus based on our discussion and choster for the related and detailed answer). In the question, it is mentioned that it may not be recognized as such by the person who utters it. An irish bull can have oxymoronic, self-contradictory or paradoxical elements in it but it is actually an absurd statement, so it differs from more general terms like oxymoron or paradox.

An Irish bull is a ludicrous, incongruent or logically absurd statement, generally unrecognized as such by its author.

The addition of the epithet Irish is a late addition.

The "Irish bull" is to the sense of a statement what the dangling participle is to the syntax. A jarring or amusing absurdity is created by hastiness or lack of attention to speech or writing.

Example:

"He'll regret it till his dying day, if ever he lives that long."

"Red" Will Danaher, in The Quiet Man

^{http://en.wikipedia.org/wiki/Irish_bull}

There is a good read about irish bull in the below book:
The God of Ordinary People: A Spirituality By Sean Caulfield

Solution 2:

Such quips have always been popular; recall Mark Twain on the important role of the historian as storyteller, because

Very few things happen at the right time, and the rest do not happen at all.

Groucho Marx opens his first autobiography admitting that

I was born at a very early age.

and remarks in a letter that

I don’t care to belong to any club that will have me as a member.

But they were humorists; for unintentionally humorous— or insightful— malapropsisms, eggcorns, tautologies, and paradoxes, consider Goldwynism and especially Yogiism (why not Berra-ism?), named for filmmaker Samuel Goldwyn and baseball manager Yogi Berra respectively.

To Goldwyn are attributed such turns as

Anybody who goes to a psychiatrist should have his head examined.

I'll give you a definite maybe

Yogi Berra is known for saying things like Nobody goes there anymore— it's too crowded; When you come to a fork in the road, take it; and A nickel ain't worth a dime anymore. His statements have been so widely quoted and misquoted in American media that many people are unaware that he originated such sports clichés as