Long one but here goes.
DH's Mum and Dad has their house repossessed, lots of issues surrounding alcohol etc. We only found out the day before the eviction happened and on the day FIL stole MIL's car and left her in the street. MIL went to stay with Family and they never spoke after that.
DH and I married around a year after that and FIL didn't turn up to our wedding, even though he spoke to DH that morning and everything was fine, and DH refused to speak to him after that.
A year later MIL died unexpectedly. She had got quite a substantial amount of money from the sale of the house and she had got her life back on track after leaving FIL. They were still married so FIL ended up getting all of MIL's money, after promising to give the money to the 3 children he changed his mind and kept it.
A year later we had our first baby, he wasn't interested in meeting the baby. His other Son got married and he didn't turn up to that wedding either.
FIL's Dad passed away a few years later, he never turned up to his funeral. Heir Hunters have tracked him down so he can claim his VERY substantial inheritance. FIL's Sister has said we should write to him to ask for MIL's money back now he has loads of money. She said that their Father had intended to change his will and leave FIL's share to his children instead of him, but he was too frail to.
AIBU to write and ask for him to give the money owed to his children and 5 grandchildren he has never met?