South Wales Police say they worked with Interpol and the Department of Homeland Security in America, as well as agencies in the UK, in putting together the case against Watkins.
DCI Peter Doyle says the pleas today do not mark the end of the investigation, and they will work 'tirelessly' to identify any other victim.
This investigation has uncovered the most shocking and harrowing child abuse evidence I have ever seen. There is no doubt in my mind that Ian Watkins exploited his celebrity status in order to abuse young children.
Today's outcome ensures that the three people responsible have been brought to justice.
The safeguarding of children has been the primary objective for the investigation team and the outcome of this investigation has been achieve through a multi agency approach at an international level.Two very young children have been removed from this abuse and given a future that would otherwise have been denied them.
More top news
Marchello Cusano, 35, died following a house fire in Llanelli on 11 April.
More than 10,000 signatures have been put to a petition opposed to plans to change NHS services in west Wales.
Soprano Elin Manahan Thomas has been chosen to sing at HRH Prince Harry and Meghan Markle's Wedding on May 19.