Hi,
Since your sister was only a permanent resident of Canada (not a citizen) at the time that she filed for divorce, the divorce decree cannot be judicially recognized here in the Philippines. As a rule, laws on status (ex. civil status) apply to Filipino citizens although they may be living abroad. In other words, since Philippines has no divorce law, a divorce decree obtained by a Filipino citizen abroad is not recognizable here.
Considering that your sister is still married to her ex, in so far Philippine law is concerned, he is still entitled to 1/2 of the conjugal properties/absolute community of properties (depending on the date of their marriage).
If your sister wants to have her marriage nullified in the Philippines, she may file for petition for nullity of marriage based on psychological incapacity (if either or both of them are found to have psychological incapacity to perform essential marital obligations.)
With respect to the properties of your grandmother, inheriting her properties will only take place upon her death.
You may also email me directly on km@kgmlegal.ph
Best regards,
Atty. Katrina