I’ve had a bit of experience wearing two. When my son, now 3.5, was younger, I watched a couple of his little friends and experimented with different babywearing techniques a lot. I found I could wear two kids in one wrapThis works best when the kids are of similar weights. That keeps the heavier child’s weight from pulling the wrap too tightly on the lighter child.
You can also wear them in two different wraps.
Neither of these are my preferrence, though. For me, the key to dual wearing is timing. I like to put the front carrier on, but NOT put the baby in it yet. A ring sling is a good option here, as is a stretchy or hybrid wrap, anything where you can put the carrier on first, then put the child in later. Then, I like to put the older child and the carrier on the back. I like a SSC (soft structured carrier) here. A short wrap is another good choice. You don’t want a lot of bulk in the front. You definitely don’t want to be tying anything over the smaller baby.
When you are putting the child on your back, you are leaning over, making your back flat as a table, while you get him situated. If you already have the baby in the front carrier, she needs to be in something that has really good head support. Even so, you are usually bouncing around a bit, getting a good seat for the heavier child. For that reason, I really prefer to put the baby on front after the back rider is all settled.
Now, you can put the baby in the front carrier as you normally would. You should have good support for both, with neither bearing the weight of the other.
I really think wearing two is underutilized by caregivers. If you are already wearing the heavier child on a regular basis, your body is used to bearing that weight. It isn’t much of a difference to add a 10 or 15 lb baby, especially if it isn’t for a long haul. Now, I probably wouldn’t go hiking this way, but it will get you through the grocery store or let you get one or both to sleep somewhat peacefully.