Charles Ellicott Commentary 2 Samuel 13:3

"But Amnon had a friend, whose name was Jonadab, the son of Shimeah, David`s brother; and Jonadab was a very subtle man." — 2 Samuel 13:3 (ASV)

Jonadab, the son of Shimeah. —In 1 Samuel 16:9, Shimeah is called Shammah, and appears there as the third son of Jesse. He had another son, Jonathan, mentioned in 2 Samuel 21:21, as the conqueror of one of the giants. The word subtle is used simply to indicate sagacity and wisdom, whether rightly or wrongly exercised.