For the past several hundred years, England has dominated their smaller island neighbor, Ireland. Not all of the Irish are too happy about it - there have been many revolts against the Protestant rulers of Catholic Ireland. Sadly, for the Irish, these have all failed due to a variety of factors.
More recently, since the worst of the Famine has passed, men and women of the True Gaelic Blood are working together, with the help of friends across the seas, to throw off the yoke of English tyranny. They call themselves the Fenian Brotherhood (yes, even the women). To the people of Ireland, they are heroic figures, risking all to free their Emerald Isle. To the English, they are bloody-minded terrorists and anarchists, murdering hooligans and rabble-rousers.
Fenian agents can be found in all parts of the solar system, doing their best to make trouble for the British, raise funds for their own activities, or hiding from the law. Their Brotherhood is dedicated to weakening the Empire to the point that the next general uprising will finally be successful.
Some VSF universes allow for a Republic of Ireland already in existence. Even so, Fenian agents work against the threat of invasion from England and re-occupation. So you can still have loads of fun with these fellows, usually as villains in the typical Anglo-centric VSF gaming campaign.