Let's say Alice is married to Bob. Alice died. Is Alice's mother still referred to as Bob's mother-in-law? Let's say Alice also had a brother Charlie. Is Bob still referred to as the uncle of Charlie's children?
In other words: does the title survive the death of the family member whose marriage created the relationship in the first place?
Edit to add: I just want to add that individual families will do whatever they feel is right based on their situation. I'm asking about the technical definition.