That's an over-reaction. Regression to the means would mean that any off-spring that Tom S might have had would almost certainly be more intelligent than he is. If we throw in fact the fact that impregnating a member of the opposite sex requires you carry out a series of tolerably complicated actions in the right sequence, the chance that Tom S actually has any off-spring is pretty remote, even if his wife or opposite sex partner has got children.
At the very least you ought to do genome testing before erasing anybody on the basis that they were part of the Tom S bloodline.