I'll cast my vote for daughter's sharing their mother's image set since it makes more sense than the current method and most more logical alternatives are far less practical, but may I add that perhaps it should only be a chance (a high chance though, say 75-90%?) that they do share the image set, and, if possible, make the next generation of kids (the incest ones) have a low (maybe 15-25%) chance of sharing the image set (even if their mother didn't, you know recissive traits and all), though I may be getting a bit too complicated by now.