Shishman dynasty
Ivan Asen
The youngest son of tsar Ivan Alexander by his marriage to Sarah-Theodora and a younger brother of Ivan Shishman. On surviving miniatures he is shown with the imperial title — a co-tsar alongside his father.
Biography
Ivan Asen was the youngest son of Tsar Ivan Alexander from his marriage to his second wife Sara-Theodora, and a younger brother of Tsar Ivan Shishman.
While still a child he was proclaimed co-emperor alongside his father: in the surviving miniatures of the age — including the famous Tetraevangelion of 1355/56 — he is depicted with the imperial crown and title. This reflected Ivan Alexander's practice of binding the crown to all his offspring, distributing the imperial dignity among his sons.
Sources
“Иван Асен … е по-млад от Кера[ца] Мария и Иван Шишман … има царска титла.”
— The Asen Family (1186–1460): Genealogy and Prosopography, p. 234