twins!

This is the second time in a month that I have discovered twin Gerbera daisies growing in my flowerbeds! Two blooms on a single stem, joined in the center. In these two cases, the twins grew from different plants, in different flowerbeds, on opposite sides of my house, but both yellow plants. None of my red or orange plants are doing this. Anyone know how common this is in Gerbera daisies? I didn't know twin flowers could even happen.