My Irish grandfather fought for the Brotherhood.
My English grandfather was a member of the Plymouth Bretheren and joined the Black and Tans rather than go to the Somme.
After the war my English grandfather was so ashamed of his part in the fighting (including a shoot out with my Irish grandfather, both unwounded -poor shots?) that he told no-one what he had done for 60 years.

There is one island, surely common sense dictates that it should be one nation.