F is for Family.
Does the character have one? How did he/she grow up? I put this under family and not children or childhood because it extends into adulthood. A character who grew up with a family who did not give a crap about her may not give a crap about anyone else. She could defend people who cared for her as a child or exhibit vengeance toward them if they did not.
If she has a child, this will change how she reacts to other people and things in the story and affect what actions she takes. Her reactions will differ from someone who doesn’t have kids, even someone who may be protective toward younglings. Most mothers would fight a ravening grizzly to the death to keep their little ones from harm. Other moms might be too high to care.
You can also have a character hook up with a surrogate family. A great number of people consider their friends their families, either because they’re too far away from blood relatives, estranged from them (or don’t know who they are), or none of them are living.
And of course, when a character forms a long-term romantic partnership, he or she creates a family. It may not contain children, but the two together are now a unit. For someone who grew up on his/her own, this could provide all kinds of readjustment for a writer to explore.
This leads me to another point. The events of your story should dictate whether your character has a family, too. In Rose’s Hostage, I deliberately chose to alienate many of the characters from this kind of relationship to increase their vulnerability. Libby, the hostage, has no family at all; all her relatives are dead. Her best friend Jade is like a sister to her and is in a serious relationship herself. Libby has tried to form a romantic attachment, only to have it blow up in her face. When we meet her, she’s bored, directionless, and ripe for the picking.
Along comes Joshua the bank robber, who has no family ties either and whose one attempt to create them ended fatally. Libby is vulnerable to the capture bonding that occurs when he kidnaps her. Despite Jade’s attempts to support her, it’s not enough to prevent what happens. (I’d love for you to find out what happens, if I ever get my manuscript back and get it published. Rawr!) Joshua becomes vulnerable to her as well, which proves a huge (and deadly) distraction.
Bonds with coworkers can affect the story too. Example: When Skye in the TV show Marvel’s Agents of S.H.I.E.L.D first joined the group, she tended to be sneaky about stuff and fly by the seat of her pants because she was so used to being completely on her own.
Now that she’s more a part of operations and Agent Coulson (love him!) is offering her stability and guidance, she’s starting to open up and work more collaboratively with them instead of going her own way (i.e. behind their backs). She’s becoming one of the S.H.I.E.L.D family.
In turn, Skye has begun to mean something to them. If you watched the “T.A.H.I.T.I.” episode where
she gets shot and they go to the underground bunker to get the drug used to bring dead Coulson back to life,
(By the way I figured out how to do this, haha!)
you will have seen what lengths her new family will go to in order to help her. Adversity is a good tool with which to build relationships in a narrative, and so is a common goal that characters share.