Honesty in advance would not necessarily help.
I know of a couple, the H died 15 years before the W. No children. Each had 2 siblings, and all 4 siblings were married with families. The wills stated that the surviving spouse would inherit all, and when the survivor died, all would be split equally 4 ways between the 4 siblings.
By the time the W was terminally ill, the H's siblings were very elderly and one was widowed; none needed anything. They had 3 DCs and 4 DGcs, all comfortably off.
The W's siblings were younger but less fortunate. One was retired, reasonably comfortable, had a DS (single, no family) and a DD (single, one son). One sibling had died, leaving a widow but no will, so his share was split among his 3 DCs, who could all have used some extra money.
One of the W's siblings tried to persuade the W to change her will, as things had changed a lot in the 15 years since her H had died, but she refused. You could tell her sibling felt some resentment towards the H's wider family, who needed the money less.
Discussing in advance would only have distressed the W. It was her wish, and that of her late H.