Shimeah - Called Shamma (marginal reference), was Jesse’s third son.
Subtil - literally, wise. The word is generally used in a good sense, but here, and in Job 5:13, it means crafty.
Related Commentaries of 2 Samuel 13:3
2 Samuel 13:3
3 But Amnon had a friend, whose name was Jonadab, the son of Shimeah David's brother: and Jonadab was a very subtil man.