What to Look For in a double travel buggy, Similarityapp says,

A side-byside double with small footprint (for narrow doors and on public transport). Add carrycots or seats (with adaptors) to increase the frame's weight capacity for children up to 50 lbs.

Budget best double strollers with front and back suspension for uneven surfaces. Large storage basket, padded handlebars, and large storage basket.

Size

Double pushchairs are generally wider than single ones, especially when they are side-by-side buggies such as the Kolcraft Geo 3 or UPPAbaby. This extra width allows them to accommodate larger children without straining their chassis. They also have other important features that make them stand out, including generously-sized pop-out canopies with SPF 50 and peekaboo windows; swivel lock front wheels which help navigate narrow spots such as aisles for shopping; a one-parent cup holder and an innovative fold mechanism that can be done by one hand; and 10 inch back wheels that aren't designed for rough terrain but can are able to handle city streets and theme parks fairly well.

In terms of cost these kinds of lightweight buggies, which are side-by-side, are surprisingly affordable.

Weight

The heavier the double buggy the lighter it is, the easier it is to lift and maneuver. The Joie Evalite Duo is a great option if you need to be aware of weight, since it's the lightest we've seen in our lab tests, but it still has plenty of features, including large pop-out canopies that come with SPF 50 and windows that peek out and a quick-release fold that stows flat within seconds; four-wheel suspension that can handle rough terrain and a swivel front wheel that makes navigating narrow aisles in supermarkets and shops easy. It's also extremely affordable at over a thousand dollars. It can also carry twins or a baby and toddler with the purchase of an additional'sidepack'.

Flexibility

A good double buggy can provide a lot of flexibility, regardless if you have twins or an infant and a toddler. Narrow tandem buggies are a great way to squeeze through small spaces. Side-by-side models let you to keep the track of your children and keep them safe while you are navigating the grocery store or in the park. There are many buggies that come with a variety of seat configurations that allow you to modify them as your children develop, and some offer the option of adding a ride-on board or car seat.

The Joie Evalite duo is an excellent example. It can be used to hold two seats or a car-seat. The adaptors make it easy to convert from a single seat to a double in merely seconds. It has a large pop-out canopy sunshade that has UPF 50+ protection, adjustable legrests and peekaboo window in both seats. A standing fold is simple to do and quick.

Tri-fold buggies such as the iCandy Peach are another versatile choice. Their slim frames are perfect for narrow aisles and doors while they are able to accommodate twins or even a baby and an adult due to the addition of UPPAbaby's 'PiggyBack' board (which you buy separately). They offer a generous basket, and come with all the extras you might require, such as rain covers and liners.

Tandem buggies typically have children seated together, which can make them easier to push and more robust on uneven surfaces but can be tricky to maneuver up and down kerbs. They have a larger footprint than a single-seater and may be too large to fit through doorways.

Comfort

This is one of the most comfortable lightweight doubles that we have examined. It has stadium-style seating on both seats, ensuring that your children can take in the view. It also features a large UPF 50+ canopy with a peekaboo window, a padded toddler seat with an additional RumbleSeat that comes with built-in adjustable leg and foot rests, as well as an integrated cup holder for a single parent. The seats recline independently by pressing a lever under each seat. The testers also appreciate the fact that the straps can be secured and unfastened in one hand. The handle is easy to turn making it easy to fold. It can also be stored by putting the backrest up to make it easy to access.

With 30 different configurations (it'll carry twins as well as a toddler and baby or three kids if you add the option of a 'PiggyBack' board) this is a fantastic option for families who are looking to expand with their child. Its large shopping basket and soft suspension mean it's good on streets and in cities too. It's also reasonably priced. BabyGearLab recommends this product for youngsters up to the age of six.