One of my favorite historical romance authors is Eloisa James. In the back of one of her books, and for the life of me I cannot remember which, she addresses why all the heroines of that series (her Duchess in Love series, I believe) were such close friends. I can’t remember exactly what she said since it’s been so long since I read it, however, the gist was she thought every heroine needed a close network of friends to turn to for support or to make her see reason.
I completely agree with her logic. Now, not every heroine can have a close group of girlfriends or sisters, of course. However, if it’s possible to give the heroine a sister or two or a close girlfriend, excellent secondary characters can develop.
During the first chapter of my current book, Intentions of the Earl, both of the heroine’s sisters’ are mentioned. One in a way that makes the heroine (and probably the reader, too) want to strangle the breath out of her. And the other in a distant, mysterious way. As the story goes on, the relationship between the three sisters comes to light, and though all three have drastically different personalities, it’s clear that when together, they’re close.
Liberty, the youngest sister, comes across a lot as exacting, stiff, and quite frankly, a pain in the hind-end at times. Yet, Brooke knows, and even mentions several times that under it all, Liberty has a heart of gold. One instance where we see a hint of the heart of gold hidden behind the shield of propriety in the drawing room when some unflattering information is spilled about the hero in Brooke’s presence. Though only a simple gesture, it’s enough to know there’s more to her than just a cold, unfeeling person who’s bent on being proper at all times.
Quite the opposite, Madison, is just as much of an ignorer of the rules as her our heroine, but hides herself from the outside world behind a cloud of uncertainty and distance. To nearly everyone in society she seems disinterested and indifferent, but when alone with her family, she’s different. Maybe not seen so much as implied, she has a tendency to enjoy saying (and perhaps listening to) things better left alone.
Her closeness with the heroine is undeniable throughout the story though. In several places, she offers Brooke a pillar of support when she needs it most in a way that’s sympathetic and compassionate, a stark opposite to the vibe she gives off the to outside world.
I think one reason why sisters or girlfriends are an excellent source of secondary characters is because though we’ve not know them for an extended period of time, the heroine (or alternatively, brothers and close male friends for the hero) has. The relationship between them is not being developed, just explored. With exploring a relationship and not building one (like with a hero/heroine that have just met) a different side of secondary characters can be seen to help them grow and develop or set them up for future books.