His mother was Maria Răreșoaia of Hârlău, whose existence is not historically documented but who is said to have been the wife of a wealthy boyar fish-merchant nicknamed Rareș "rare-haired" (i.e. bald).

Then the over-zealous Petru, deserted by his own boyars, his capital Iași ablaze, and faced with a Turkish-Tatar-Polish army headed by Suleiman the Magnificent, who was bringing Ștefan Lăcustă to the throne, had to flee to his Transylvanian fortress of Ciceu.

The voivoda Petru raised his head in revolt, but my horse's hoofs ground him into the dust, and I conquered the land of Moldovia.

[1]It is said that, during this flight, Rareș wandered for two weeks in the impassable forests of Transylvania, with difficulty making his way through spiny vegetation and ancient bushes and trees.

It took over two years and various political changes in Transylvania and Moldavia before Petru was able to gain the sultan's forgiveness and regain the Moldavian throne in early 1541.

Nor could he take back the Budjak, occupied by Sultan Suleiman, nor even the citadels of Ciceu and Cetatea de Baltă, except as simple fiefdoms (which he did in 1544), for their walls had been razed by George Martinuzzi.

He lent the head of the proposed crusade, Joachim II of Brandenburg, 200,000 florins, but the initiative was abandoned when Buda was besieged in 1542 and Rareș died, still a Turkish vassal, on 3 September 1546.

Aided by his wife Jelena, he built and repaired numerous churches, including in Baia, Botoșani, Hârlău, Târgu Frumos and Roman.