The House of Velvet and Glass: Katherine Howe

Interestingly enough I have read all three of Katherine Howe's books and they all had something to do with witchcraft. In this one the father can trace lineage to a New England witch and he can see the future. The little sister and mom were on the Titanic trying to find a husband for the sister when the ship went down. The eldest sister had been spurned by her beau and the story follows her as she realizes she too has her father's gift. The war starts right when her little brother starts getting into trouble and is kicked out of college. She knows he will die in the war, but if he doesn't he will live miserably and eventually commit suicide. The story ends with her brother being remembered as a hero and the main character getting married.