IANAL but from my interpretation of the situation....
Section 67(4) of the Succession Act states that the estate will be distributed in equal shares:
The electronic Irish Statute Book (eISB) comprises the Acts of the Oireachtas (Parliament), Statutory Instruments, Legislation Directory, Constitution and a limited number of pre-1922 Acts.
www.irishstatutebook.ie
You'd then look to Section 55. The personal representative(s) has the power of appropriation but that might be a moot point here as there is just a house and no other material assets:
The electronic Irish Statute Book (eISB) comprises the Acts of the Oireachtas (Parliament), Statutory Instruments, Legislation Directory, Constitution and a limited number of pre-1922 Acts.
www.irishstatutebook.ie
Can you give more detail on what the siblings might intend to do?
Do they wish to allow the sibling living there to continue living in the house? Is the sibling a dependent relative? Could the others use a pure disclaimer where their shares go back into the estate and allow the sibling living there to potentially avail of Dwelling House Relief (if applicable?)