MS 23211, possibly of the late 9th century, makes him a son and successor of King Æscwine.
The post-Conquest historians Henry of Huntingdon (Historia Anglorum), Roger of Wendover (Flores Historiarum), and Matthew Paris (Chronica Majora) substitute the name Eorcenwine (Erkenwine, Erchenwine) as his father.
Though their testimony is centuries removed from Sledd's floruit, it is thought that they drew on alternative pre-Conquest material.
On no known authority, Roger of Wendover and Matthew Paris state that Sledd directly succeeded his father on his death in 587.
Seaxa is perhaps identical to Seaxbald, father of king Swithelm, of unknown placement within the royal family, but Yorke thinks this unlikely on chronological grounds.