There are several popular scenarios that are often used as a backstory for characters in fantasy worlds, in Role playing like DnD and in LARP. Backstories can go as far as you want them to. It's not uncommon for enthusiasts to write half a book as a character's backstory. Backstories can also be put together really quickly and easily, check out the most popular examples below.
It's important to keep in mind that when you're LARPing or playing with a group, your backstory fits into the bigger picture and is in agreement with the partners you're playing with.
Orphan
A role playing character who lost their parents as a child and grew up without a traditional family. This can fuel their motivation and desire for adventure or revenge.
Exiled hero
A character who for some reason has been banished or cast out from their homeland. They're looking for a way to restore their honor or to build a new life.

Apprentice of a mentor
A role playing character who has been trained by an experienced mentor or teacher. They've gained valuable knowledge and skills, but may also have obligations to their mentor.
Heir to a destiny
A role playing character who is the heir to an important legacy, such as a kingdom, a magical artifact, or a family responsibility. This can put them in a position of power or in conflict with others.
Seeker of lost knowledge
A role playing character who is on a quest to find a lost book, a forgotten ritual, or other valuable knowledge. Their curiosity drives them forward.

Refugee from a war
A role playing character who has fled their homeland due to war or conflict. They carry emotional baggage and may be involved in political intrigue or rebellion.
Tempted by dark forces
A role playing character who struggles with the temptations of dark magic, curses, or inner demons. They may be plagued by a dark side and must fight to keep their moral compass intact.