In Ontario, marriage automatically revokes a will. The moment I sign my marriage documents this October, it will revoke my current will; I could choose to revive it later, but I would have to deliberately do so. The rationale for this is that a spouse or future children should not be accidentally disowned because of a will that was done prior to the marriage, or even prior to the relationship.
If you divorce, your will is not revoked, but it is treated as if your former spouse died before you. Any gift to your ex-spouse will be invalid, and he or she cannot act as your executor if he or she is named. However, the rest of the will stands. If you named your wife, with your brother-in-law as an alternate, your brother-in-law will still be able to act as executor. If you named your husband as your sole beneficiary, with the alternate being half your family and half his, then his family is going to still get half your estate. Given this, most people will want to update their wills after a divorce.
The really tricky one is when you are separated, but not divorced. If you have a formal separation agreement, it may state that you each renounce any interest in the other’s estate. If you don’t have a separation agreement, or if it doesn’t release any interest in each other’s estate, for estate purposes, it is as if you are still married and your spouse will inherit from you if you die. If you are separated, regardless of whether you have a separation agreement in place, it is very important to update your will as soon as possible – or make one if you’ve been putting it off.