In Spain, women do not change their surnames upon marriage, and children get the surnames of both parents. Parents have always been allowed to choose the order of the surnames, but the default has been to put the father’s name first. (And in cases of dispute, the father’s name always goes first.) A new law will alter this, making the default order the alphabetical one.
Critics said it would endanger surnames whose first letters are at the end of the alphabet. These will gradually be relegated to second place on the surname list and not be passed down to grandchildren
For more, go here. (Thanks, Mr Jender and Jender-Parents!)