At some point his mother seems to have poisoned all of Ariarathes’ five brothers; but the infant king was saved by people loyal to the dynasty and had Nysa killed.

Using this as a pretext, his maternal uncle, King Mithridates V Euergetes of Pontus (150 BC–120 BC), tried to assert control over the country by marrying Ariarathes to Mithridates' first daughter, Laodice of Cappadocia, who was also Ariarathes' maternal cousin.

Nicomedes III was soon expelled by Mithridates VI, who placed upon the throne Ariarathes VII.

[4] However, he still continued to mint coins of himself wearing a diadem only, while coins of him wearing a tiara was mainly used on his tetradrachms, which implies that it was probably done with the purpose for the grandees and kings of Armenia, Commagene, Pontus, and possibly Parthia, to see it.

[4] The modern historian Matthew Canepa (2017) suggested that Ariarathes VI minted these two different types of images "to promote both cultural backgrounds in the numismatic medium intended for the army, court and foreign circulation.