Apollodorus Library 3.5.6

[6]
  Zethus married Thebe, after whom the city of Thebes is named; and Amphion married Niobe, daughter of Tantalus, ¹ who bore seven sons, Sipylus, Eupinytus, Ismenus, Damasichthon, Agenor, Phaedimus, Tantalus, and the same number of daughters, Ethodaia ( or, as some say, Neaera), Cleodoxa, Astyoche, Phthia, Pelopia, Astycratia, and Ogygia, But Hesiod says that they had ten sons and ten daughters; Herodorus that they had two male children and three female; and Homer that they had six sons and six daughters. Being blessed with children, Niobe said that she was more blessed with children than Latona. Stung by the taunt, Latona incited Artemis and Apollo against them, and Artemis shot down the females in the house, and Apollo killed all the males together as they were hunting on Cithaeron. Of the males Amphion alone was saved, and of the females Chloris the elder, whom Neleus married. But according to Telesilla there were saved Amyclas and Meliboea, ² and Amphion also was shot by them. ³ But Niobe herself quitted Thebes and went to her father Tantalus at Sipylus, and there, on praying to Zeus, she was transformed into a stone, and tears flow night and day from the stone.