Have you ever read "Life As We Knew It" or "The Dead & The Gone" by Susan Beth Pfeffer?
But then in the 3rd book, that i'm re-reading now; we're back to Miranda and her family. They are doing well (and by well, i mean still devastated..but alive) Her brothers Matt and Jon go to the Delaware River to catch fish and Matt comes back with a new wife: Sylvia. they decide to get married and Syl tells them about how people travel in "bands" and travel on foot and sometimes hitchhike on FoodTrucks. Then Miranda's dad and step-mom (Lisa) arrive with their new born____(dont want to ruin it for ya!) and their "band" that band happens to include Alex (the boy from the 2nd book) and his sister Julie. Anyways....I'll let you read