We done our own probate on our fathers estate last year. One of our siblings died very shorty after him, but was included in the probate as a beneficiary, though she was unmarried and had no children. She died without a will. After probate our fathers estate was then divided among the remaining 2. Now we are doing our siblings probate. For the purposes of CAT thresholds from sibling to sibling, does our deceased siblings estate include the 1/3 share of our fathers estates which she would have received, or does that revert to our parent to child CAT threshold, which is well in excess of each share of our fathers estate. I ask because the split of our deceased sisters share of our fathers estate was below the sibling to sibling threshold, about 29,000, so perhaps for that reason there was no tax request, but does this mean we have mostly used up the sibling to sibling threshold, even though this was our fathers estate. I'm convinced we will have to effectively pay 33% CAT tax of that third of our fathers estate which reverted to us, as our siblings estate exceeds the small sibling to sibling threshold of 32,500. Am I correct in this?