Suleiman II
Suleiman II (April 15, 1642 – 1691) was the sultan of the Ottoman Empire from 1687 to 1691. The younger brother of Mehmed IV, Suleiman had spent most of his life in the kafe (cage), a kind of luxurious prison for princes of the blood within the Topkapi Palace (it was designed to ensure that none could organize a rebellion).
When he was approached to accept the throne in after his brother's death by assassination in 1687, Suleiman assumed that the delegation had come to kill him and it was only with the greatest persuasion that he could be tempted out of the palace to be ceremonially girded with the sword of the Caliphs.
Hardly able to take control of events himself, Suleiman nevertheless made a shrewd choice by appointing Ahmed Faizil Köprülü as his Grand Vizier. Under Köprülü's leadership the Turks halted an Austrian advance into Serbia and crushed an uprising in Bulgaria. During a campaign to retake eastern Hungary, Köprülü was defeated and killed by Imperial troops led by Louis William of Baden at Szlankamen in 1690. The Sultan died a year later.
The Osmanli Dynasty ruled the Ottoman Empire from 1281 to 1923, beginning with Osman I (not counting his father, Ertuğrul), though the dynasty was not proclaimed until 1383 when Murad I declared himself sultan. Before that the tribe/dynasty might have been known as Söğüt but was renamed Osmanli in honour of Osman.
The sultan was the sole regent and government of the empire, at least officially. The sultan enjoyed many titles such as Sovereign of the House of Osman, Sultan of Sultans, Khan of Khans, Commander of the Faithful and Successor of the Prophet of the Lord of the Universe. Note that the first rulers never called themselves sultans, but rather beys. See the article on state organisation of the Ottoman Empire for further information on the sultan and the structure of power.
Hereditiary heads of the House of Osman since 1926:
When Mehmed II (the Conquerer) took over Constantinople on May 29, 1453, he committed a coup d'état by replacing the
Emperor of the Roman empire (a.k.a. the Eastern Roman Empire a.k.a. Byzantine Empire) with himself. He took the title Emperor (imparator)and protector of Orthodox Christianity.
He let himself be crowned Emperor by the Patriarch of Constantinople Gennadius Scholarius, whom he protected and whose stature he elevated into leader of all the Eastern Orthodox Christians.
So in addition to being Sultan of the Muslim citisens and Khan of the Turks, he was now also styled Emperor of the Romans.
As emperor of the Romans he laid claim to all the Roman territories and succesfully managed to put most of the Roman territories (except Rome and Italy) under his own control.
