Septimus Julius Weasley and the Unbreakable Vow

This is the reason why any D/G ship is disgusting and would never happen because well, the unbreakable vow is the reason why. This actually happen in Arthur past's and he undertook the vow. In order to avoid either the Malfoy has to be blood chromosomally adopted into another family or the Weasley groom/bride has to be blood chromosomally adopted into another family.