no.
Genesis is the story of creation and at the time of creation, the population of the world was low, so people had to marry those related to them to grow as a race of people. God knew that they could handle that biologically, because genetics of the individuals was much purer then, since there wasn't so far to come from the orginal creation, Adam. By the time Dueteronomy was written (some thousand or so years after creation,) the world was much more populous, and therefore it was uneccessary to marry close relatives, and again God knew this (and he also knew that it would start to lead to biological issues.) The Dueteronomy law doesn't contradict the previous laws, it supercedes them.
Not a contridiction.
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