Who was the first wife of the Prophet, may Allah bless him and grant him peace, and did any of his wives remarry after his death?

The Prophet Muhammad, peace be upon him, first married Khadijah bint Khuwaylid. None of his wives who were under his conjugal bond at the time of his death married anyone after him. This is forbidden by scholarly consensus and is a unique characteristic of the Prophet, as they are the Mothers of the Believers in this world and the Hereafter.

As for those whom the Prophet, peace be upon him, separated from during his lifetime, scholars differed on the permissibility of their marrying others. The correct view is that it is permissible. It is reported that the woman from Banu Kalb whom he separated from was married by Ikrimah ibn Abi Jahl or Al-Ash'ath ibn Qays.