וּלְאַמְנ֣וֹן רֵ֗עַ וּשְׁמוֹ֙ יֽוֹנָדָ֔ב בֶּן־שִׁמְעָ֖ה אֲחִ֣י דָוִ֑ד וְי֣וֹנָדָ֔ב אִ֥ישׁ חָכָ֖ם מְאֹֽד׃
But Amnon had a friend, whose name was Jonadab, the son of Shimeah David’s brother; and Jonadab was a very subtle man.
Read Kabbalistic (mystical) interpretations of II Samuel 13:3: Zohar and classical Jewish mystical sources, free online.