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
Soldiers from 1st Battalion Welsh Guards have overseen the planting of 2,000 oak trees to mark the centenary of the Battle of the Somme.
Wales meet Belgium in a Euro 2016 quarter-final in Lille on Friday night.
Gareth Bale insists reaching the last eight of Euro 2016 is not enough for Wales ahead of their quarter-final against Belgium.