Kinship and Greek Heroes

I should be forbidden from camera-ing
so many crooked shots of doom.
(Farnese Hercules at The National Gallery)

One of the things I find really fascinating in Classical Mythology is the familial bonds between heroes and how little emphasis is placed upon them. It's so strange to think of these other heroes as siblings and cousins to one another. So often we don't have any understanding of those bonds in the stories that surround them. Pirithous and Theseus are an exception, in some respects, since we know from more than one source that they were like brothers -- but their relationship doesn't have anything to do with their shared lineage or the idea that they're cousins. They bond over their perceptions of one another as honorable and equals in strength and cunning and bravery.

We never hear about Heracles calling up his half-brothers or sisters, or really forming relationships with his blood-relatives on his divine side. Sure, he might have buddied up with Theseus to hit on the Amazons, and there's that whole Jason and the Argonauts thing, about which we will not speak, but even when Euripides showcases the friendship between Theseus and Heracles, there isn't any mention of their familial bond. They were friends and heroes in arms, but not explicitly spoken of as cousins, either.

Of course some of the heroes are from different generations, and not at all contemporaries -- like Pirithous and Perseus, for example, or Heracles and Perseus* -- so in that case, it's a lot less strange that there's no mention of any relationship they might have shared. But Pirithous and Heracles were contemporaries AND brothers, and I'm not sure I know a single myth in which they cross paths at all. So as I read, and write, I wonder: what might Pirithous have thought of his famous brothers, living and dead? Did he consider them kin at all? And if not, why not?

*Perseus is actually an ancestor of Heracles as well as his brother. Alcmene, Heracles' mother was Perseus' granddaughter. So in this case, one would think there would be even more of an acknowledgment of that family connection. But. Not so much. Then again maybe being the great-grandfather and brother of Perseus crossed some incestual line of weirdness for the Greeks, so they just kind of tried to ignore it.