In the fall of 2014, before C could walk, we spent a lot of time with her in a baby carrier. Truth be told, she spent a lot of time on our backs even after she could walk. (She still loves the occasional ride on Daddy's back.)
When the girls were small babies and could only be carried on our fronts we could get away with wearing an extra large coat and zipping it over us both. As soon as they could switch onto our backs we were out of luck.
As coats are too bulky to be worn inside the carrier, I started to look for coats that could be worn over two of us. The few babywearing coats I could find were either prohibitively expensive (many times what I spent for my really good winter coat) or thin polyester fleece numbers.
And thus I made my own.