It's actually quite common with TGA strains.. Jacks Cleaner II and JTR are two that I have seen this first hand. In my experiences tho, the twin wasn't viable. This time however I believe the twin is going to make it just fine. I shall document my results!
i recently had twins but I felt that the little twin was going to impede the growth of the "main" plant and i couldn't really figure out how to separate them as you did as my twin was a little deformed