With the deposition and death of Charles III without legitimate children, the principle of a united secular western counterpart to the (Eastern and Orthodox) Roman Empire became purely theoretical, and later claims to universal sovereignty over Latin Europe were rarely taken seriously.
However, Charles III did have a bastard son, Bernard and much of his reign prior to his deposition was taken up with securing legitimization for the putative Prince, a plan in which he was opposed by several bishops and supported by Pope Hadrian III, who died before he could order the deposition of the opposing Bishops led by Bishop Liutbert of Mainz and his party. Had Liutbert been removed from opposition, it seems fairly likely that the Emperor would have won over the remaining Bishops in the realm.
Had Bernard lived to adulthood, and been crowned as Emperor, and had heirs, it's possible that the forces driving nascent nationalism in the two primary Frankish kingdoms would have sputtered out and the Holy Roman Empire could have retained its control of West Francia along with East Francia, Middle Francia and Lombardy.
However, I can find no reading in Salic law that supports or opposes the full succession of a legitimized bastard. Much later, French law would provide support for illegitimate children. Roman law in the early Principate seems to have been very flexible, but I don't know if that lasted into Late Antiquity when the Franks would have come in contact with it.
So, had Bernard been legitimized, would his authority or right to rule be recognized by his father's vassals, or would the Empire still have split apart?
However, Charles III did have a bastard son, Bernard and much of his reign prior to his deposition was taken up with securing legitimization for the putative Prince, a plan in which he was opposed by several bishops and supported by Pope Hadrian III, who died before he could order the deposition of the opposing Bishops led by Bishop Liutbert of Mainz and his party. Had Liutbert been removed from opposition, it seems fairly likely that the Emperor would have won over the remaining Bishops in the realm.
Had Bernard lived to adulthood, and been crowned as Emperor, and had heirs, it's possible that the forces driving nascent nationalism in the two primary Frankish kingdoms would have sputtered out and the Holy Roman Empire could have retained its control of West Francia along with East Francia, Middle Francia and Lombardy.
However, I can find no reading in Salic law that supports or opposes the full succession of a legitimized bastard. Much later, French law would provide support for illegitimate children. Roman law in the early Principate seems to have been very flexible, but I don't know if that lasted into Late Antiquity when the Franks would have come in contact with it.
So, had Bernard been legitimized, would his authority or right to rule be recognized by his father's vassals, or would the Empire still have split apart?