There were 2 medieval Vlach rulers who converted to Islam directly from the throne -

Iliaș Rareș of Moldavia in 1551 (grandson of Stephen III the Great & despot Jovan Brankovic)
Mihnea Turcitul (=Turkified) in 1559 (5th gen direct descendant of Vlad III Dracula)

Both took the name Mehmet & were immediately promoted to higher positions in Ottoman hierarchy - Iliaș as bey of Silistra & Mihnea as bey of Nicopolis. It seems to be no coincidence that those beys has also the mission of keeping an eye on Moldavia & rsp Wallachia

However, both of them were unable to maintain those positions for more than a few years & have been subsequently demoted & exiled.

Iliaș was poisoned in 1562 in Aleppo, Syria. Mihnea died in 1601 either in Tripoli,Libya or C-tinople.

Iliaș did not marry (was homosexual & had a Turkish lover).

Mihnea was left by his wife Neaga who went with their children to Peter the Lame (Mihnea's uncle) at Suceava & while his mistress Vișa left to Venice at one of Mihnea's maternal aunts with his son, future Radu Mihnea.

* Mihnea's conversion was in 1591 ( Twtr still has no edit function to fix small typos!!! )