Daniel and Jessica Groves could be anyone. Without additional context, they might be regular people going about their daily lives, or they could be known in a specific community, field, or family, but we don't have enough information to be certain.
No, it's not a common expression. Most often, we hear about general time frames like a year or six months to write a novel, but 738 days is rather specific and not typically used widely.
Dear Enemy was a novel by Jane Webster. This novel was a continuation of Daddy-Long-Legs. It recorded the life of the protagonist, Judy, in the form of letters. The story tells how Judy revived the orphanage after she became the director of Grier Orphanage and developed a troubled relationship with Doctor Feng. This novel was one of Jane Webster's works. She was the granddaughter of the famous American writer Mark Twain and one of the famous American novelists.
I'm sorry, but without more specific information, I can't provide the full story of Daniel and Jessica Groves. There could be many people with these names, and more details are needed to tell their story.
In fact, 'Old Town in the Green Groves' is not a true story. It's a work of fiction that might draw inspiration from various sources but doesn't represent actual happenings.