03/05/2015 09:39 am ET Updated May 05, 2015

8 Inarguable Reasons Writing A Book With Your Sister Is A Great Idea

Some would say the act of writing and the act of sisterhood are two different beasts, to be kept in two different containers, like Japanese fighting fish. But we undertook the task of merging the two 12 years ago, and all for the love of a story called Sisters of Shiloh. Now, on the eve of our first published novel together, here are eight reasons why writing a book with your sister could never be a bad idea:

1. Diverging interests = ample inspiration.

Kathy: Becky is a history freak. Ah, I mean, history enthusiast. She's watched North and South like, eighty times. And she once accused me of being a "robot" when I refused to cry watching Braveheart. I've never cared much for history, myself. I just wanted to write a book with my sister, so I asked her for an idea. She said she was always fascinated by the real women who fought disguised as men during the Civil War. Women actually did that?! A novel was born.

Becky: Kathy IS a robot. Who could watch that movie and not get weepy? But she's an amazingly talented and creative robot. I love her writing and was so excited to get to work with her and learn from her. Well, actually I first told her that I thought writing a book together would be a great way for us to never speak to each other again. I remember what it was like sharing a bathroom growing up...

2. You know someone has your back... most of the time.

Kathy: Becky is my little sister. Therefore anything that went wrong, I could blame on her. And anything that went right, I could take all the credit for. Just like childhood!

Becky: Kathy is my big sister. I was a first-time writer. Working under Kathy's protective eye would mean anyone who unfairly criticized me would be pummeled much like Lisa Snodgrass when she pushed me off of my bike in second grade.

3. You can divide and conquer.

Kathy: Becky's an avid researcher. Sisters of Shiloh was not a novel that invited you to just scratch the surface. The Civil War apparently takes some research, I found out. She and her Navy pilot husband were moving for a year's duty assignment in England, but spent a month in Maryland. She used that time touring battlefields and researching in archives and generally annoying librarians, archivists and park rangers, which, as a little sister, she was particularly good at.

Becky: Kathy's an incredible creative mentor. We bounced ideas off of each other and worked out the outline of the basic story, then I worked to find the historical resources to help fill in the story. What regiment did they join? Where did they fight? What were the movements of the regiment? Kathy and I poured over all of the materials we could find about the female soldiers, especially a great book called The Fought Like Demons, and one called All the Daring of a Soldier. We talked on the phone every day and shot emails back and forth about different ideas for the characters.

4. You always have a travel buddy (for better or worse).

Kathy: Becky's amusing to travel with, when she's not yapping about the history of every place we pass. She dragged me to Maryland and Virginia. But I did think it was great to be able to walk the same battlefield that served as a pivotal scene in the early part of the novel. Becky was very outgoing, finding Civil War buffs and experts to interview. I slept a lot.

Becky: Kathy's great fun to travel with, when she's not pretending to be asleep. We spent a week researching at Antietam and in Winchester, Virginia. We even got to stay at the Piper Farm on the Antietam Battlefield.

5. You never have to worry about being polite -- because you're sisters.

Kathy: Becky is fascinated by an ocean of historical minutia. After several months of bombardment about gory battle details, I began to drink. She apparently found other ways to clear her mind and got unexpectedly pregnant.

Becky: Kathy and I have a lifetime of history between us. Like when she used to drag me to her bed because she was scared of the dark, then booted me unceremoniously out at the crack of dawn. Good times!

6. And because you're sisters IRL, it's easy to write about sisters and bring them to life on the page.

Kathy: Becky and I love each other. We used our feelings about each other as sisters to fuel the sisters' narrative in the book: that combination of protectiveness and affection and the struggle to be understood. I, myself, would follow Becky into war. I know she would do the same for me. I just wished her selfish pregnancy hadn't interrupted the book.

Becky: Kathy wants readers to feel like they are actually there with the characters. What kind of cups would they use? What kind of fish were in the creeks? What kind of flowers were in bloom? It's her use of these details that makes her writing so vibrant.

7. You always have a partner to sweat it out with...

Kathy: Becky is patient. We took Sisters of Shiloh to market...and could not get a publisher. I was crushed every time Becky asked in her hopeful voice: "Have you heard anything?" Ten long years passed, years in which we rewrote, revisited, and finally put it aside. I went on to publish two more novels myself, and found the love of my life, while she had seventeen more children. Or maybe it was only three more -- it's hard to tell when they swarm.

Becky: Kathy never gives up. After ten years I was sure that this book would never see the light of day. But one day a few years ago, her new husband asked her why she didn't dust off that old novel we'd put so much work and passion into. She was skeptical, but something made her take another look. She had her old agent back -- Henry Dunow, the best agent in the world that she had once fired in a conniption (wisely, she had crawled back). He showed the first half to Jenna Johnson at Houghton Mifflin Harcourt, and she bought it after reading just half the manuscript.

8. And, most importantly, you always have a built-in drinking buddy biggest fan.

Kathy: Becky's a great cook. Just saying.

Becky: Kathy's fun to drink with. Ask anyone.

And so here it is... Sisters of Shiloh, our first collaboration. We're having a grand time together promoting the novel. And we're already thinking about the next book. Becky has this idea...