As proven by vlogs made by individual Sidemen members, the majority of their fans are 12 year old males. Whilst some females fans do exist, their numbers are unfortunately significantly smaller.
The Fans Edit
Thankfully, the majority of the fans are loyal and respectful. Not all of them are 12, and the groups content is enjoyed by a wide demographic. However, the surprising number of underage fans makes content creation somewhat difficult. Luckily, the Sidemen have not conformed to this fact and still include adult themes within their videos (in particular is KSIOlajideBT who regularly references sex and masturbation within his videos - to a somewhat extreme extent).
The majority of the fanbase are British (primarily due to the fact that the group themselves are British) although the group has fans from almost every country on the planet.