After the birth of Henry, despite weak evidence, Siemowit ordered his wife strangled and the boy cast away from his court, and raised by a peasant family.
After several years, Siemowit's daughter from his first marriage, Margareta, then wife of Casimir IV of Pomerania, decided to rescue her brother and took him to her mansion in Słupsk.
Nonetheless, possibly driven by feelings of guilt, he convinced his other sons to agree that if Henry would ever abandon the way of priesthood, they would share his inheritance with him.
Siemowit did not accept this and, as the Polish kingdom was weakened and in a state of disarray after the death of the King of Poland (Louis I of Hungary), he took control of the disputed parish with his army and occupied it for several years.
In 1391, Henry, who was known both for his incredible strength and his diplomatic skills, accepted a mission from the hands of the king of Poland, Władysław Jagiełło.