His existence is known from two sources: one is a mummy-label found on the mummy of his daughter Nebetia, where he is mentioned as her father; the other is a Saqqaran relief of his tutor, Meryre, where a person named Siatum is depicted sitting on Meryre's knee.
Siatum's identity is confirmed by two accounts: a label on the mummy of Nebetia, stating he was her father; and an image from Saqqara showing him seated beside his teacher, Meryre.