We had another client recently who received a windfall; her former husband hadn’t updated his will, and they were separated without a separation agreement and not yet divorced, so she inherited everything on his sudden death.
I can just about guarantee you that that is not what he wanted.
In Ontario, divorce doesn’t revoke a will; it simply removes the divorced person from the will. So, if you left everything to your spouse, alternatively to your brother-in-law, he’s going to inherit even if your former spouse won’t. If you’re separated without a separation agreement, what’s in the will stands, and also, your spouse can inherit if you don’t have a will at all.
This is one of the situations where you absolutely must update your will. You can change it again after you have your separation agreement in place, if anything needs to be in there once the paperwork is all signed, but you must protect yourself now.