Guernsey is one of the Channel Islands in the British Isles. It is not part of the United Kingdom.
The island is notable among the Sidemen community due to the fact that it is the birthplace of Harry (a.k.a Wroetoshaw). This makes determining Harry's true nationality somewhat difficult, since the island is not technically part of the United Kingdom of Great Britain and Northern Ireland, yet is still a part of the British Isles.
Harry grew up and lived with his mum, dad, brother and sister on Guernsey until 2014 when he moved to the Stratford Halo in London.
One of the most common stereotypes related to Guernsey is the fact that its population is inbred, and all families living there are a result of incest. The Sidemen regularly joke about Harry having sex with his siblings and his fans have begun to pick up on this.
More recently, as proven in Cards Against Humanity sessions, a new stereotype affiliated with the island is the idea that its residents mate with animals such as goats and sheep. Harry has admitted that he has no idea where this idea came from, and it is thought to exist purely among the followers of the YouTubers.