I guess I worded that wrong, your correct, but with sibling to sibling you have a higher chance than offsring to parent. I couldn't go into this in depth as I havnt ever bred sibling to sibling to find out what could possibly happen. Although I could go into the genetics of morphs easily, I can't seem to word what im thinking correctly and without being able to do that idk how to help. Im sure if you've worked this out and seen what could possibly happen, then you know more about genetic deformalities than I. This is certainly a topic in which is hard to discuss unless you have done countless studies to see which is worse, parent to offspring or sibling to sibling. Im sure someone who has learned more about this than I will step in and help figure this out.