She’s Having a Baby by Suzanne Jenkins

Devon Lyon has the perfect life. With childhood friend Mike Saint, they follow a long line of Saints into the fire academy, including Mike’s uncle who is the battalion chief. After graduation, Mike meets the love of his life, nursing student, Aisling Murphy. The last thing she has time for is marriage, so she talks Mike into living together. Then, right before fire season, she finally agrees to marry Mike, and the worst wildland fire in California history changes life for Devon and his best friends, the Saints.