Help creating a backstory for a knight cleric/paladin

My DM is planning a sequel campaign that takes place in, and a player at our table wants to play as the granddaughter of my last pc who ended up as a queen of trade and the leader of the thieves' guild in the city she resides in, overthrowing the last one.

I'm making a character who's a servant/knight of the granddaughter who grew up together, but I'm drawing massive blanks on how to flesh out my pc. All I have is that their parents were people my last pc helped during the last campaign who became her knights over the years, and that she inherited her oath to the house from her parents. I'm also having trouble mixing the paladin/cleric(haven't finalized the class choice yet) in.

What I know of the other player's backstory is that they are the spoiled granddaughter of pc who was sent on a quest to actually learn some actual life experience by her grandmother if she wishes to inherit the family sword and treasures. They initially formed a 3 Musketeers-type team with other nobles they grew up around, but that fell apart.