Sons of a snake

Both Alexander the Great and P. Cornelius Scipio Africanus the Elder were said to be sons of Zeus (respectively Jupiter), the god having taken the shape of a giant snake to impregnate their mothers. It's difficult to judge which part Alexander and Scipio themselves had in the fabrication of those legends. According to Plutarch, Alexander asserted his divine parenthood when he was talking with Asians and Egyptians, but not with Macedonians and Greeks. Scipio never asserted it, but never negated it either. Moreover, Scipio was familiar with the Greek culture, so he might have just copied Alexander's legend for his own political reasons. Also, Alexander's legend might not be completely unrelated to the legend of Buddha's birth, notably the part where his mother dreams about being pregnant of a powerful animal.

The theme of the great general son of a god in the Indo-European history and mythology would be interesting to explore. I don't see what role does the snake symbol play in this system, but it reminds me a bit of the Celtic Melusine.