The romance presents Erbin at the point when age has become a problem for his lands. His authority still matters, but neighbouring chiefs know that he is growing weak and begin to threaten his possessions. The wider tradition associates the family with Dumnonia in south-western Britain; the homecoming episode in Guest's translation specifically names Cornwall. It does not supply a modern boundary map or a dated administrative history. The immediate concern is the protection of the territory that Geraint will inherit.

Erbin's envoys reach Arthur's court at Caerleon and explain the need for Geraint to return. They address Arthur on behalf of a kinsman and subordinate ruler, describing Erbin as the king's uncle within this version of the tale. Arthur is reluctant to lose a valued companion, while the queen's household is sorry to part with Enid. Nevertheless, he agrees that Geraint should protect his own lands rather than remain at court solely for the glory of tournaments.

Geraint and Enid depart with an honourable company. The journey leads towards the Severn, and Erbin's people meet them on the far side. Nobles and members of the household welcome the returning son and his wife. A feast brings together the chief men of the country. The celebration matters because the change of ruler is a communal act: Geraint does not simply find an empty throne and claim it. His father's authority and the acceptance of the people prepare the transfer.

On the following morning Erbin tells Geraint that he has maintained the dominion while he was able, but that his son must now preserve it. Geraint answers that he would rather leave the power with his father and remain at Arthur's court. Erbin refuses to postpone the change. The distribution of gifts comes first, followed by arrangements for the subjects to give homage. They express their willingness to receive Geraint, and the young ruler begins the work of visiting and securing his boundaries.

Erbin's decision creates the setting for the later trials of Geraint and Enid. The son who has accepted public responsibility must also negotiate the demands of marriage and reputation. The tale returns to their adventures rather than giving Erbin a separate final battle or death scene. His principal action remains the decision to yield authority. The crown used to symbolise him represents that transfer; the episode does not require a literal scene of an old man placing a crown into another man's hands.

Other Welsh material preserves the family through names rather than a continuous biography. Culhwch and Olwen lists Geraint, Ermid and Dywel, called Dyvel in Guest's spelling, as sons of Erbin. Genealogical tradition calls him Erbin ap Custennin and connects the line with Custennin Gorneu. Those names should not be used to collapse every Arthurian Constantine into one ruler. Poetry about Geraint at Llongborth and the seafaring triad belong to the son's wider reputation, not independent proof of Erbin's reign. His enduring place is as the father whose peaceful transfer turns an Arthurian knight towards the needs of his own people.