Inheritance Tax - descretionary deduction for Siblings?

[Blue123]

When both parents have passed away and one child has lived at home all their life, never married or moved away but child 2 did leave and are equal inheritors are they still both liable for full inheritance tax or, would the sibling that had remained in the home be awarded a form of discretionary tax deduction. The property will not be sold and will remain the home for child 1 whom will reach an agreement with child 2.