My grandfather married a woman who was my father's stepmother, and he would inherit from her as a son only while my grandfather was still alive. After my grandfather's death, the stepmother officially became legally (tax-wise) the same as a foreign woman, even though she had been a grandmother to my sister and me for four decades. If she had signed over the flat to my sister and me by gift deed, we would have had to pay the full tax, even though we have been her grandchildren all our lives...