He could hurt you or your children
I have two schizophrenic siblings. Neither of them have ever, or ever would be, violent toward another person, so I find this sort of knee-jerk response infuriating. Schizophrenia does not always result in violent tendencies.
However, with all the experience I have of schizophrenics, and it's obviously a hell of a lot, there is no way, ever, that I could have either of them ever come to live with me. It's time consuming, it's draining, it's exasperating and wearing to sit up till 3am calming and trying to reason with someone who is having delusions.
OP you say you are not in the UK so there is less support than someone here could access. If I was in your position, and knowing what I know, I'd canvass his friends and family for a regular monetary donation to pay his rent on a flat (is there a benefit system where you are?) I would consider some financial support for him a small price to pay to keep your own home your oasis of peace.
In the long run, it's doing him a disservice to let him get his feet under your table and then let it all go pear shaped. Better to get him established in his own place where you can keep your eye on him from a distance.
Of course, this is all only from my own personal point of view.
My siblings may have more extreme schizophrenia than your bil.
But it would be a No from me. It's hard enough to deal with it from a distance, let alone live with it.