Estate Tax

According to Oasis.gov.ie website:

"A threshold of 46,673 euro applies to gifts/inheritances made by a person to his/her parent, brother, sister, niece, nephew, or grandchild. In certain circumstances, a parent taking an inheritance from a child can qualify for the 466,725 threshold. "

Does anyone know what those "certain circumstances" may be?

death (i.e. not gifts)

i am single and have no spouse to leave my house and money to apart from my mother and brother. if the limit is only 46000 for each they will be taxed heavily.

Is there any way to avoid this?