Fields of Grace (Heart of the Prairie #4) by Kim Vogel Sawyer

With their eldest son nearly to the age when he will be drafted into military service, Reinhardt and Lillian Vogt decide to immigrate to America, the land of liberty, with their three sons and Reinhardt's adopted brother, Eli. But when tragedy strikes during the voyage, Lillian and Eli are forced into an agreement neither desires. Determined to fulfill his obligation to Reinhardt, Eli plans to see Lillian and her sons safely settled on their Kansas homesteadand he's equally determined that the boys will be reared in the Mennonie faith. What he doesn't expect is his growing affection for Lillianand the deep desire to be part of a family.