The link shouldn't be very hard to find.
1. I was born a commoner, but I succeeded my father as King.
2. I was the second King of our dynasty. Strangely enough, the Kings in our family always only fathers one son.
3. I was an Emperor. During my reign, a religious leader was born in the realm.
4. I was not Royal at all. On the contrary, I was the King's opponent and had hi executed. But even though I was not a Monarch, my son succeeded me.
5. I was the eldest amongst five siblings. We all died before we could marry ahd have children. I died on the same day as my parents.
6. I am a Prince. My grandfather was a King. My father has four children. I'm the youngest of them.
7. I am a Prince. My parents had 15 children. I'm one of the younger children. I died before the 15th child was born, but I outlived their 14th child.
Who are we, and what do we have in common?