Wait, wait, wait, the assumption that So6p had children after becoming the Jinchuriki might be wrong and from what we know, it probably is. Think about it, a child of someone with the Fruit's power was as strong as So6p (before becoming the Jinchuriki), but children of someone with the Fruit's AND the Jyuubi's power are weaker or equal even when combined ? This doesn't make sense, which probably means that only the power of the Fruit was passed to his sons and for that to be the case (basing on other children of Jinchuriki) means that So6p had children before he became a Jinchurki. Another possibility is that the Fruit's power was completely used up, which would mean that the Sons got only the Jyuubi's power and not it's Fruit (the first option sounds more probable).