What duties did princes have in ancient Japan?

Hello, I'm currently researching government in ancient Japan and have come across a few things that I find rather obscure. Perhaps someone can help me? Were all princes descendants of the emperor? What were their responsibilities? I'm aware that they held political positions, but to what extent did they "actually" rule? Should I imagine them…

Which royal family would you want to come from if you were born around 1860?

If you had to choose, which European royal family would you want to come from between 1860 and 1920? Because you have to think about the World War and your social status, and as a woman, you also have to think about your marriage prospects…what would be best? (provided you do not become the king/queen…