Throughout their time with Hades, players will get a chance to know Zagreus' eccentric and often overbearing extended family. The game places a lot of importance on these familial connections, being sure to always refer to Zeus and Poseidon as uncle or Hermes as Cousin, but there are some strange connections within that Supergiant has so far chosen to ignore. This is probably for the best as these family ties are very taboo in today's society, but to the ancient greeks they weren't uncommon. This results in a few characters having multiple different connections to the main character, Zagreus.
In case fans haven't read up on the Olympian creation myth yet, it quite frankly has a lot of incest. Given that there are so few gods involved at the start of creation, many of the well known gods that players have come to know are actually the result of inbreeding. Especially when it comes to Zagreus, there are some very odd connections. Minor spoilers ahead for the main story of Hades, as exploring Zagreus' family ties is integral to the story of the game as a whole. Until players have discovered who Zagreus' mother and grandmother are, they should turn back.
Zagreus and Persephone
It doesn't take long for fans to discover that the real reason Zagreus is trying to escape the underworld is to reunite with his long lost mother, Persephone. This concept is at the heart of the story, but Persephone and Zagreus' relationship isn't so simple. Persephone is the daughter of Zeus and Demeter, Queen of the Underworld, and Goddess of grains and fertility. This means that she is not only Zagreus' mother, but also his cousin, as she is his Uncle Zeus' daughter. In the game, she is obviously simply referred to as mother, and the question of who her father is isn't brought up.
Naturally, this has interesting implications for Hades as well. As Zeus's brother, Hades is actually also Persephone's uncle, and Persephone is his niece. This means that Hades is simultaneously Zagreus' father and his great uncle, another concept which Supergiant Games felt it was best not to explore. Granted, these sorts of connections likely wouldn't add anything to the story, rather confusing it more in an unnecessary way, but it is still very odd to think about. The relationship between Zeus, Poseidon, Hades, and Demeter is actually the basis for many of these strange family connections.
Zeus, Demeter, and Zagreus
After Demeter reveals to Zagreus that Persephone is her daughter, he puts two and two together and realizes that she is actually his grandmother. He starts referring to her as such in the game, but there are more layers to it than that. Demeter is the sister of Zeus, Poseidon, and Hades. Ignoring the obvious fact about her and Zeus' relationship then, that means that Demeter is both Zagreus' grandmother and his aunt. The same holds true for Zeus. Though he refers to him as uncle Zeus, he is also Zagreus' grandfather.
What's interesting is that Supergiant Games is presented with the same situation here twice, a character that is a grandparent and an aunt/uncle at the same time, but chooses to take different approaches in each scenario. This is most likely because Zeus is more well known as the brother of Hades than as the father of Persephone, but it's odd nonetheless. It seems as though Supergiant Games doesn't explore this relationship in the game, never revealing the fact that Zeus is in fact Zagreus' grandfather as well, leaving fans to wonder who Persephone's father actually is in this version of greek mythology.
Zagreus, Megaera, and Thanatos
No disrespect to Dusa, but Zagreus, Megaera, and Thanatos form the game's most iconic love triangle, All of these characters are embroiled in a complicated romance that evolves overtime throughout the game, but they also have interesting connections through one character in particular, Nyx. Within the lore of Hades itself, only one of these characters is directly related to Nyx, that being Thanatos, but in greek mythology there are a few more connections as well. In the game, Nyx is Thanatos' mother, Zagreus' foster mother or step mother, and Megaera's supervisor of sorts.
There are some sources that link Megaera and the other furies as being direct descendents of Nyx, and given Zagreus' connection with her (believing her to be his mother all this time), it spawns some interesting romances. As far as Zagreus knew, Meg and Thanatos were his sister and brother in a sense, as it's only after he discovers Persephone that he discovers that isn't the case. This makes the romance options in Hades, especially with Thanatos, that much more awkward, as Zagreus would have only recently found out that he was not directly related to the character. Meg's situation is different, though, as in the game her lineage isn't specified.
Zeus, Dionysus, and Zagreus
Though it's already been covered that Zeus is Zagreus' uncle and grandfather, there is yet more to uncover in this relationship. Zagreus is actually one of the more misunderstood and confusing characters in greek mythology, with his lineage and role in the realm of the gods changing from account to account. In some cases, he is believed to actually be Dionysus, and in others, he is the son of Zeus and Persephone. The Dionysus connection isn't ever mentioned in the game, but the confusion about Zagreus' father is actually hinted at.
After giving enough nectar to Zeus, he will make a joke about how it seems that Zagreus is closer with him than with Hades. He continues on to say that they should spread the word that Zagreus is actually Zeus' son, though nothing comes of this. This is an obvious nod to this confusion regarding Zagreus' parents, but opens up a whole new can of worms. If Zagreus were in fact Zeus' son, that would make Zeus both his father and his grandfather, perhaps the most disturbing connection yet. In that regard, Persephone would then be Zagreus' mother and his sister, so choosing to stick with Hades as the father is a lot more comfortable for modern audiences.
Hades is available now on PC and Switch.