“Tamar.” An important name in David’s family, going all the way back to Tamar, who was married to Jacob’s son Judah’s oldest son Er, but ended up having a child in David’s line by Judah himself (Gen. 38). David named his daughter Tamar, and Absalom named his daughter Tamar (2 Sam. 14:27).
“and Amnon the son of David fell in love with her.” This “love” was not actual love, but simply animal lust. Amnon, being the oldest son of David and the crown prince, was spoiled and could not control his desires. The rape of Tamar by Amnon was the start of the fulfillment of Nathan’s prophecy to David that the sword would not depart from his house and evil would arise from his own house (2 Sam. 12:10-11).