I can posit one scenario wherein two people genetically related would not share a related language -- when an outside influence completely supplants one of the groups' language. For example, a number of native American languages have gone completely extinct, with the former users now employing English while some of the languages related to the extinct languages are still spoken in certain areas of the country.
I've notice one of the features of your "theories" is that they do not take into account the overall picture; it's as if you took a snapshot of a pine tree, then declared all trees to be pines based upon your snapshot.
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