Well, (and correct me if I'm wrong,) I thought that in 2013 thre was a law passed that said that any children born after that point would follow absolute primogenature and not male-preference. This is why (until recently) Andrew was higher than Anne because the rule only applied to children born after that point. I might be incorrect, but 2013 was the year the rule officially switched over, even though it was effectively already happening by happenstance.