Tvrtko I of Bosnia
Real power in northern Serbia was held by Prince Lazar. The latter did not assume the imperial or royal titles (associated with the House of Nemanjic), and in 1377 accepted king Tvrtko I of Bosnia (a maternal grandson of Serbian king Stefan Dragutin) as titular King of Serbia. Serbia proper became a vassal of the Ottomans in 1390 but remained effectively ruled by the Lazarevićs and then by their Brankovićs successors until the fall of Smederevo in 1459.