✔ 最佳答案
They follow different religions which brings with different customs. The British are Anglican/Church of England, the Spanish are Roman Catholic.
Succession to the throne is now different. In Spain male-preference primogeniture means sons are ahead of daughters in the succession; Britain it is now absolute primogeniture by age rather than gender which is in line with most of the other European monarchies.
In the UK if the Queen does not approve the potential spouse of someone in the succession they lose their place. In Spain, both the parliament and the king would both have to disapprove a match for that to happen.