After the death of his father in 1441, John I and his younger brother Henry X inherited the Duchies of Lüben and Haynau as co-rulers.

The death of Elisabeth of Brandenburg, Dowager Duchess of Brieg-Liegnitz in 1449 left in jeopardy the future of the Duchy of Liegnitz.

John I and Henry X were the legitimate heirs of that land, as grandsons of Duke Henry IX of Lüben, elder brother of Duke Louis II, Elisabeth's late husband, who left her Liegnitz and Brieg (already give by the Dowager Duchess to both brothers in 1443) in 1436; in addition, John I had another claim over Liegnitz through his marriage with Hedwig, youngest daughter of Louis II and Elisabeth.

However, the brothers never took possession over the Duchy: shortly after Elisabeth's death, the local nobility rebelled against the Piast government and sought the help of Emperor Sigismund, who placed Liegnitz under the direct sovereignty of the Kingdom of Bohemia.

One year later (1450) the still hard financial situation forced them to pledged Brieg to their maternal uncle, Duke Nicholas I of Oppeln.