Offspring, a novel, was published by Zoland Books in 1995.
From Publishers Weekly:
Lincoln and Isabella (Izzy) are former 1960s activists now living in the suburbs with their three sons, Obadiah, Malachi and Zephaniah. The couple raises the children as if they’re in a simpler, idealized era, and, while the boys attend the local school, they don’t socialize with their peers, choosing instead to spend most of their time with their dog, digging a tunnel beneath the house. The tunnel project is encouraged by Lincoln and Izzy, who like the boys’ interest in at-home activity-at least until one of the teachers begins hinting that the boys have been involved in vandalizing school property. Soon, events force Lincoln to confront the tunnel, his children and his own family past. Strong, a professor at Tufts University, has created a strange assortment of characters that are intriguing …. the descriptive details of the boys’ imagination and adventures keep a reader’s attention in this unsettling family drama.
You can find it at Amazon here.