The primary source which confirms his parentage has not yet been identified. The Chronicle of Adémar de Chabannes specifies that "Ramnulfus…comes Pictaviensis" was "consanguineus…Willelmi…comitis Arvernis". The Chronico Richardi Pictavensis also states that "Ramnulfus consanguineus erat Willelmi Pii Aquitanorum Ducis et Arveniæ Comitis". The relationship between Rainulf and Duke Guillaume has not yet been traced.
The name of the wife of Comte Rainulf II is not known with certainty. "Gauzberto comite, Ramnulfus comes, Ermengarde…" subscribed the charter dated Apr 878 under which "Gauzbertus comes" donated property "in pago Santonico…in villa…Dorodonno" to the church of Saint-Hilaire de Poitiers. Richard suggests that Ermengarde must have been the wife of one of the named counts because of the order of the signatures. Richard rejects the hypothesis that Adda "coniunx Ramnulf", whose tomb was discovered at Saint-Hilaire de Poitiers, was the wife of Comte Rainulf II.
After the death of Rainulf's father in 866, he and his brothers were deprived of their inheritance. It appears that no-one was at that time installed as Comte de Poitou, the county being administered by Louis King of Aquitaine, son of Charles II "le Chauve" King of the Franks. He appears to have been finally installed as RAINULF II Comte de Poitou in , judging by his heading the list of confirmants of his brother's Apr 878 donation to the church of Saint-Hilaire de Poitiers. After the death of Louis II "le Bègue" King of the West Franks, Comte Rainulf had custody of the late king's youngest son Charles, who later succeeded as Charles III "le Simple" King of the West Franks. After the deposition of Emperor Karl III in Nov 887, Comte Rainulf claimed the succession to the kingdom of Aquitaine and supported the candidature of Guy of Spoleto as King of the Franks.
He was appointed Duke of Aquitaine in 888. Regino names "Ramnulfum et fratrem eius Gozbertum et Ebulonem abbatum de sancto Dionysio" when recording their battle against "Waltgerius comes" in Jul 892.
The Chronicle of Saint-Maxence records the death in 890 of "Ramnulfus comes Pictavinus", but the year is incorrect if Regino correctly names Rainulf in Jul 892. 2