How did the children of Adam breed? was it incest?
BTW As I know only problem for brother and sister to have a child is mutations in DNA. If Adam and Eve had original DNA without mutations then their children could make healthy grandchildren.
Of course, there is no separate Islamic 'take' on this matter. There would only be one possible theory for this highly controversial question,
It was incest back then according to today's definition of incest.
There is nothing wrong in accepting the fact that God ordered Prophet Adam (pbuh) to marry his sons with his daughters. (Stories of the Prophets)
It was in the very beginning of the mankind when God ordered so, so that mankind will expand through its natural system of reproduction.
But, later when there started ego and jealousy, God devised rulings accordingly and banned incest.
Please note that, God always wishes the welfare of the mankind and he revises/abrogates his previous rulings as and when deemed necessary.
May the creator guide us all.