In any case, the chronology does not appear favourable. If he had been King Bosons uterine brother, he could not have been more than ten years old at the time, which is incompatible with his bearing the comital title.
Gingins-la-Sarras hypothesis cannot be dismissed entirely. However, it is a convoluted interpretation of the otherwise simple statement in the Annales Bertiniani that Richard was King Bosons brother.
Unless further information comes to light in other sources, it is suggested that the simple explanation is the best.
An agreement dated Feb 876 of Charles II "le Chauve" King of the West Franks names "Bosonisducis et sacri palatii archiministri atque imperiali missi, Richardi comitis" as present in Italy with the king, although it fails to specify the family relationship between them He presumably assumed the role of his brother Boson as missus in Italy in early 877, when the latter was recalled by Emperor Charles II.
A charter dated 5 Sep 918 records the restitution of res Sancti Nazarii sitas in villa...