Buying a Tandem Double Buggy
A tandem double buggy can be a great choice if you have twins, or children who are close in age. They're a bit smaller than side-byside buggies, and ideal for maneuvering tight spaces, such as entrances, on public transportation and on rough terrain.
Many convert into travel systems to include two carrycots or car seats. However, they are heavier and longer than single pushchairs, and may feel less stable as they bump up kerbs.
Convertible
There are a variety of options for adding a second seating or converting a single twin stroller with car seats to a thule double stroller. The UPPAbaby Vista V2 is a large, gorgeous stroller that easily converts from a single model to double buggy with carrycot by incorporating the rumble seat (available separately). It is more expensive and less maneuverable because the second seat is positioned in front of the first seat. Nuna Demi Grow is a similar model but lacks storage underneath the seat when it is used as a double buggy with car seat stroller.