Is That A Single Portion Or A Double Portion?

Whilst there is no legal obligation on any parent to leave their estate to their children in equal shares or indeed to leave it to their children at all if they have reached the age of majority, it is often the case that parents do treat siblings the same and siblings certainly expect to be treated equally.  How does this affect the distribution of your estate upon your death if, having made a will treating your children, on an equal basis you then make a gift in favour of one of them in preference to the other during your lifetime or perhaps gifts to all of them but in differing amounts?  Undoubtedly, the disappointed sibling(s) is likely to seek to suggest that allowance be made when distributing the estate for gifts already received during the parent's lifetime.  Does the sibling(s) that has received a lifetime gift from their parent receive both that gift and an equal share of the estate?  This is where the double portions rule is likely to be effective.