yellowraincoat
Oh that's interesting to know, I wasn't aware of that possibility.
I have to say that all the Northern Irish friends I have, have chosen the Irish one and that is also their only one, but that really has to do with their convictions about their heritage, culture and religion, so they would and they do, perceive themselves as Irish only who happen to be born and living in the "North of Ireland".
I also have close Scottish friends who clearly identify as Scottish first and British second and dear English friends who sort of not only identify as English, but also sort of like to use England, GB, and UK interchangeably, however it's more habit than not knowing the geographical/political/historical facts
.
But none of the above would sing the anthem, due to the various reasons mentioned here, and also thankfully my English friends have lots of sensibility and abilities to self-reflect their culture and their country's legacies (positive and negative), like many, many on this thread thankfully.