Stolen money!!!💰💵

Hey ya’ll. One of my parents passed away a few years ago. My oldest sibling was in charge of the estate. He did not distribute the funds correctly, but more importantly there is a massive amount of money missing. I do have a lawyer and we are attempting to retrieve parent’s bank statements. Does anyone have any tips/tricks or suggestions on how I might prove oldest sibling took a bunch off the top? He was in control of all accounts at the end as the parent was ill.