She was the eldest daughter and heiress of John of Caesarea and Alice de Montaigu, and both of her parents came from the upper echelons of the nobility of Outremer.
In his Assizes of Jerusalem, the jurist John of Ibelin records that his cousin, the lord of Caesarea, refused the bailliage of Jerusalem in 1243, and instead the Haute Cour gave it to Queen Alice of Cyprus.
Since her father was dead, this is probably a reference to her husband, John Aleman, indicating that she was already ruling Caesarea by then.
[1] In April 1249, Margaret and John sold six casalia to the Teutonic Knights.
Margaret's eldest son and heir, Hugh, died in a riding accident in 1264.