Baldwin IV of Jerusalem
Reginald was the son of Gerard of Sidon and Agnes of Bures, and a grandson of Eustace Grenier. He first rose to prominence in the Kingdom in 1170, when he married Agnes of Courtenay, who had been married three times before: firstly to Reginald of Marash, who left her a widow; secondly (possibly bigamously) to Amalric, Count of Jaffa and Ascalon and future King of Jerusalem, with whom she had two children, Baldwin IV of Jerusalem and Sibylla of Jerusalem; and thirdly to Hugh of Ibelin, her fiancé or husband before her marriage to Amalric. Her marriage to Amalric was annulled in 1163 when it was discovered that the two were related within the prohibited degrees of consanguinity. Some writers have claimed that the marriage between Agnes and Reginald of Sidon was annulled as well, as they were related within the prohibited degrees, but this is based on a misinterpretation of William of Tyre, who says Gerard discovered the relationship between "the two aforementioned people". However, this must be referring back to the marriage of Agnes and Amalric: Gerard was dead by the time of Reginald's marriage. In December 1179, ""Agnes, Countess of Sidon" and "Reginald of Sidon"" witnessed a charter together: there is no evidence to suggest they were not still a couple. (See Hamilton, "The Leper King &amp; his Heirs" for further discussion of this.)