Probate Application taking a long time due to contesting of frivolous claim against sibling co executor. Brother contesting deceased (2018) mother's 2010 Will with frivolous claim of "suspicious reimbursement" Mother made to his USA resident sister for Mother's request to see daughter. Mother deemed compos mentis 4 mths prior to death & signed $14K AU bank transfer reimbursement in front of 2 bank executives. Trouble started when brother assumed EPOA after father's 2017 death without his older sisters (in USA) knowledge or receipt of EPOA decision. Sister has AU/USA citizenship & now has legal representatiive in NSW attempting to defend Mother's will.( 50% distribution to each sibling) Brother now seems to be amending reason to contest will to remove sister as co executor & expected to charge $150K expenses for mother 10 mths custodial at home care. Brother is wealthy, has no interest in beneficiary distribution - want to revenge sister living overseas. Mother wanted dog to be transported to daughter in USA, daughter is trying to get transport arranged, brother baulking at attempts until sister is removed as co executor. No financial information has been shared with sister, estate is $850K AU approx. from sale of home after father's death in 2017. What can be done to move this difficult situation forward to conclusion as stated in valid will?