A 53-year-old Guelph man is now facing a total of 21 charges in relation to a number of alleged sex offences.

Guelph Police announced Thursday that four more charges have been laid against William Smith due to more allegations being uncovered.

All the alleged victims are underage.

Among them are three young siblings, according to their mother, who cannot be named to protect the victims’ identities.

The mother claims the incidents involving her children occurred in 2010, but says her children have never opened up about them.

“I had no idea until (CAS) showed up at my door,” she tells CTV News.

At the time, the mother says she was told there wasn’t enough legal evidence to pursue the case.

Now, Smith faces seven charges of sexual interference, six charges of sexual assault, three charges of mischief, two charges apiece of possessing child pornography and invitation to sexual touching, and one charge of making child pornography.

Police want to hear from other potential victims – and so does the mother.

“Children are going to be scared and not wanting to come forward, thinking they’re in trouble – but whoever this happened to needs to come forward,” she says.

Police say all the alleged victims were known to Smith, who will appear in court next week.