Came across this in Ravi Zacharias' sermon recently. He apparently believes it, made the allusion that because David saw Bathsheba from his porch, Ahithophel advised Absalom to rape David's concubines on his porch.
There are contest to this fact, that Ahithophel and Bathsheba are related. However, the best the Bible could give was to tell us the name of Bathsheba's father was Eliam (2 Samuel 11:3), and Ahithophel's son's name was Eliam (2 Samuel 23:34).
Therefore, should one belief that the Eliam mentioned in those verses are the same person, as well as affirm Ahithophel's identity in 23:34, the it would be true. And the revenge against David would be more dramatic than I had thought.