my mother's best friend went through a horrible similar situation.
My mom's friend is Shirley. Her mother died and her father (Carl) remarried when he was in his 70s. The woman he married (Mable) was also widowed, and had her own grown children.
His will, which Shirley was the executor of, and had seen while he was alive, stated that the house they lived in (which was his) and it's contents would go to his new wife if he died first, BUT would revert to HIS children upon her death. This was all nice and neatly done at the lawyers office. One copy left at the lawyer's, one at the house.
Carl died first.
Suddenly, there is no will. The lawyer says that Carl and Mabel came in about a year prior and said they needed that copy and 'were going to make a new one.'
New one was never made. Shirley never heard it mentioned (and she and her dad were very close).
So, when Carl died, there was a HUGE probate etc determining if everyone belonged to his wife, period (who clearly wanted it all to go to HER kids when she died) or his kids.
Shirley always felt like Mabel's kids manipulated the whole thing.