István was the son of Pósa Szeri but his mother is unknown. The date and place of his birth have not been found.
His wife was Klára Omori. They were married, but the date and place have not been found. Their five known children were Miklós (?-?), István (?-?), Péter (?-?), György (?-<1430) and László (?-?).
| Attribute | Date | Description | Details | Source | Multimedia | Notes |
|---|---|---|---|---|---|---|
| Nobility Title | miháldi várnagy |