Buying a Single to Double Stroller Families with two children of different ages, will need a stroller which can be converted from a single to a double. Experts like Katie Billingsley of Fourth Trimester Postnatal Retreat recommend looking for a model that has a range of seating arrangements. The Mockingbird Single-to-Double Stroller provides all these features and more at a the most affordable cost. As a direct-to-consumer company it doesn't have to pay retailer markups and offers an attra...