Family Tree of Sorts
England/Albion/Wessex = Artur/Arthur Kirkland
Ireland/Eire = Brighid/Brigid O'Leary
Northern Ireland/Tuaisceart Eireann = Patrick O'Leary-Kirkland (Brigid either calls him Patrick or Thuaidh (North), his brothers call him North or Patrick)
Scotland/Alba = Cal Stuart
Wales/Cymru = Bran Llywelyn
Cornwall/Kernow = Perran Tamar
Brittany/Breizh = Merry Conan
Sealand = Peter Kirkland
All the human names for OCs have some kind of historical reference; Bran is the name of a Celtic god, Brigid is the name of a saint named after a Celtic god (Brighid), Cal is taken from Caledonia, an alternate name for Scotland, Perran and Patrick are saints connected to their respective countries, and Merry Conan is a reference to Conan Meriadoc, who is the probably mythical founder of Brittany. (Note, Brittany is female.) Artur is an older form of Arthur.
Scotland, Wales, and Cornwall are England's older brothers, while Ireland is his twin. The older three adopted both England and Ireland at the same time and they have the same eyes, hence the "twin" designation. Brittany, a Celtic nation but part of France, is a cousin rather than a sibling. Northern Ireland is the younger brother of Ireland and England, and adopted by Scotland, Wales, and Cornwall. Sealand is England's little brother, and adopted by the rest of the family when he isn't being an honorary Nordic thanks to being adopted by Sweden and Finland.