Suiteng, if this is a rickroll, we won't be able to take it. Don't let us die so young...

Suiteng, you're making the right decision by filing a police report.
Being soft-hearted isn't gonna solve the problem, rather it'll get you in a bigger mess. If you really think that you don't have the heart to hand them in to the police, then do the China Embassy thing, but either way, get them out of the house asap.
The law is on your side.
1. They provided fake identification to secure a place to stay. You can't be blamed for not being able to recognize a fake IC.
2. You agreed to only one tenant, not two.
3. They pissed and crapped in the room. No harm done so far, but if you let it go on, who knows what might happen? That old woman might have some sort of contagious disease etc. That's why we impose health restrictions on foreigners who wish to stay here.
4. They faked an IC, what if the passports are fake too? No offence, but if you couldn't recognize the fake IC, what makes you so sure the passports are real? Bear in mind that the quality of fakes these days are quite impressive.
Ask anyone here who supports the weirdo and mum - will they take them in? I'm sure the answer is no.
If no one else is willing to put up with this shiat, then why should you?
My vote is no mercy.