Commentary for II Samuel 13:3

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.

Rashi on II Samuel