One of the characters in this, our second book, is based on someone my co-author and I knew as teenagers and young adults. He was a lascivious character, but smooth as satin—well-educated, handsome, and alluring--who treated us like adults. His motives may have been questionable, but we naively enjoyed the attention with no ill effects.
One of the most enjoyable pieces of the writing process—especially co-writing with someone I've known all my life—is the invention of characters who may bear some resemblance to someone in our lives. I love the process of making these old friends and/or acquaintances into something very different and only coincidentally similar in some specific way to the people we knew.
After beginning our first book (The Diva's Demise), I read strong warnings in a "how-to" book against co-writing. I am grateful that we had started down this creative path together before reading the warnings. It has been a most enjoyable process. Our second book is even better than the first.