If you are looking for a sling that will allow you to carry both of your babies together, you want to look for a sling that is simple to use with little, if no, adjusting necessary. In our experience, a pouch is the easiest sling to learn how to use. Our Adjustable Fleece Pouch is our #1 recommendation due to the flexibility of the fabric and the ease of use. In the upper photo, Mom is wearing her twin 4 week old babies in the cradle position while using an Adjustable Fleece Pouch.
The other option for wearing two babies together is a padded sling. Our recommendations are either a Kangaroo Korner Padded Sling or an OTSBH. If you are on the border between sizes, you may need to select a size larger than you would typically wear in order to accommodate two children. Please contact us for sizing guidance if you have any sizing questions. 
You can expect to be able to carry your babies together until they reach a combined weight of around 18-22#. At this point, you will need to carry them separately. Once they're old enough to be worn on your hip (generally, between 4-6 months), you can wear them at the same time, each in their own individual sling. The two combinations for this type of situation are either 2 pouches or 1 pouch and 1 unpadded sling. Some moms of multiples prefer to put the first baby in an unpadded sling, adjust it well and then throw on the pouch with the 2nd baby. While other moms prefer the simplicity of wearing 2 pouches without any necessary adjusting.
You can expect to be able to carry your babies together until they reach a combined weight of around 18-22#. At this point, you will need to carry them separately. Once they're old enough to be worn on your hip (generally, between 4-6 months), you can wear them at the same time, each in their own individual sling. The two combinations for this type of situation are either 2 pouches or 1 pouch and 1 unpadded sling. Some moms of multiples prefer to put the first baby in an unpadded sling, adjust it well and then throw on the pouch with the 2nd baby. While other moms prefer the simplicity of wearing 2 pouches without any necessary adjusting.
In the lower photo, Tanya is wearing two 5 month old babies in the hip position using two Adjustable Cotton Pouches.