There are several popular scenarios that are often used as backstory for characters in fantasy worlds, in Roleplaying like DnD and in LARP. Backstories can go as far as you want. It's not uncommon for fanatics to write half a book as a character's backstory. Backstories can also be put together very quickly and easily, see the most popular examples here.
It's important to keep in mind when larping or playing with a group that your background fits into the overall picture and is consistent with the partners you're playing with.
Orphan
A character who lost his parents as a child and grew up without a traditional family. This can fuel their motivation and desire for adventure or revenge.
Banished Hero
A character who has been banished or ostracized from their homeland for some reason. They look for a way to restore their honor or to build a new life.
Mentor's Apprentice
A character trained by an experienced mentor or teacher. They have gained valuable knowledge and skills, but may also have obligations to their mentor.
Heir to a Fate
A character who is the heir to an important heritage, 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 character who is on a quest to find a lost book, forgotten ritual, or other valuable knowledge. Their curiosity drives them.
War Refugee
A character who has fled their home country due to a war or conflict. They carry emotional baggage and may be involved in political intrigue or rebellion.
Temptation of Dark Forces
A character who struggles with temptations from dark magic, curses, or inner demons. They can be plagued by a dark side and must fight to maintain their moral compass.