I wanted to address this because I really don't like it when people make Ireland a child of Albion/Britannia. For me, it's like saying a chicken lays a duck egg. They're both birds, but ducks and chickens aren't synonymous to each other. And that's the case for the Britons and the Gaels. Or for the Brythonic Celts and the Goidelic Celts, same thing. The Goidelic culture existed long before the Brythonic culture broke off from it and started developing independantly. Having a Gael (Ireland) being born of a Briton (Albion) is kind of backwards.
And basically, I don't believe in a separate character for Hibernia. Hibernia is just the Roman name for Ireland. There is no distinct Hibernian culture and I've studied Ireland's early history very closely: There is no point where we can say that Hibernia died here and Ireland took over. For me, Hibernia and Ireland are the same character.
And while I can agree that by age appearance, Ireland would appear younger than Albion, he would still be the same age as her. It's just due to political disunity that Ireland didn't grow up physically very quickly. However, both Albion and Pictland had to deal with Roman threat so a cohesion among the tribes occurred more swiftly. The identity of the Picts and the identity of the Britons came together earlier, which is why Albion/Britannia and Pictland grew up more quickly than poor Ireland who had to watch his sisters get a more adult form while he stayed stuck in a child form.