Maddie and Ben have been dating for nine years. Their relationship is marked by contentment and affection. Maddie's younger sister, Mia, has been dating Casey for seven weeks. With a shared c'est la vie attitude, Mia and Casey are smitten with each other, and thrilled to explore the oh-so-many things they don't know about each other yet. But when they announce they're getting married and having a baby, it's news that throws Maddie for a loop.