I don't imagine the average grandparent spells out that they are including their adopted grandchildren. Say a grandparent has 5 grandchildren and 2 are adopted, and the grandparent states that he/she is leaving €10,000 to be divided between the grandchildren, you seriously can't think that the adopted children would be left out simply because the will didn't specify that adopted children are included in the bequest?
Under Section 26 of the Adoption Act of 1952, adopted children have the same rights as a natural born child of the adopted parent.