Lostprophets frontman Ian Watkins has also been charged with the possession and or distribution of indecent images of children.
Detective Inspector Peter Doyle, of South Wales Police, has urged "anyone who has any concerns or information which they think may be relevant to contact us."
He added: "Safeguarding children involved in such cases is always a high priority and as such measures have already been taken."
More top news
Mladic, now 75, was the military commander of Bosnian Serb forces in the 1990s, who fought against the Bosnian Croat and Bosniak armies.
Weather: Heavy rain and strong winds in the north
His representatives said Cassidy, who was hospitalised last week, died "surrounded by those he loved."