Firstly, hello and welcome!
I went to my first event with a backstory, but changed nations before time in, to date I’ve never had a formal backstory just done it on the fly and it’s not hindered my game time or experience, so I wouldn’t get too caught up on it. It’s a bit of fluff that in all honesty just helps us feel connected to our character. Just keep things simple and it will help you ease into getting to know them.
But Wintermark sustains losses at all battles so there is no reason not to just pick which everyone you like, I would pick something less recent otherwise it ties you down to needing to know a bit more history and didn’t allow you chance to become who you are.
You father died when you were 12, leaving behind your mother and her two children, since then you have spent your years working the farm with your mother and sister barely making ends meet, struggling through the elements. But now your sister has married and they are wanting to taking on a bigger role in the farm allowing you the opportunity to go on a voyage of discovery within yourself. Discover your true self and find your rightful place in the Empire, you venture to Anvil to start this journey and become your own independent person.
But that’s just my thought, otherwise may give you other advise.