Tuisto’s name means “twin” or “twice” (perhaps from the Proto-Germanic *twis). Was he the same as Ymir? Or Ymir’s twin? There’s no agreement but Grim suggests they were twins.
Ymir is the father of Bolthorn, who is father of Mimir and Bestla.
Tuisto aka Buri is the father of Mannus aka Bor who married Bestla. Their children are Odin aka Ingo, Vilje aka Istro, and Ve aka Irmin. Mannus is the eponymous ancestor of MAN-kind. His three sons are the ancestors respectively of the Ingvaeones, Istaevones, and Irminones, the three main divisions of the Gemanic people.
Thus far from Grimm. Then moving on to later structural analysis:
Odin kills Ymir aka Hymir. From his flesh the Earth (Jord), from his blood the sea (Njord), and from his brains the Sky (Tyr). These three can be said to be children of Odin who created them or of Ymir from whom they were made.
So. A tri-partite division of the world, as in most Indo-European religions.
Njord (Sea) marries his sister Jord aka Nerthus (Earth). They have Frey and Freyja. Jord is also married to her brother Tyr (Sky).
Tyr (cognate with Zeus and Jupiter) is the ruler of the gods until he loses his hand, and being imperfect now can no longer rule. War. Odin has learned sorcery from his maternal uncle MImir. Odin becomes king.
Odin takes Tyr’s wife Jord. They are the parents of Thor. Now we have the “Hero Twins” Frey and Thor who are maternal half-brothers like the Dioscuri (Castor and Pollux).
But Odin also marries Jord’s daughter Freyja aka Frigg. This is why Odin learns sorcery from Freyja, as well as from Mimir. Also why Freyja takes half the dead. Partly because she is Odin’s wife and partly because sorcery and half the dead are her inheritance as heir of Ymir. (Alternatively, Frigg and Freya are confused in a different way. It could be Frigg who takes half the dead and knows sorcery.)
Speculation from Jackson Crawford: he thinks Heimdall might be same as Ull.
Then one of the comments on that video he says:
Jumping off the Ullr/Heimdall connection I have always thought that there is some kind of connection between Heimdallr and the figure mentioned in Tacitus’ Germania known as Mannus. The reason I came to this conclusion is because of the similarity in how Mannus is said to have fathered the ancestral Gods of the three primary Germanic tribes; Irminones, Ingvaeones and Istvaeones with how Heimdallr is said to have fathered the three races of men in the Rigsmal.
What’s curious there is there’s a clear etymological progression with the Ingvaeones and the Old English Ing/Old Norse Freyr, and as for the Irminones Irmin is given as one of Odin’s many names which, in my estimation, makes Mannus the father of Odin and Frey at least if you’re going by the earlier Proto-Germanic versions of the mythos. Of course this contradicts Snorri’s recounting of Odin’s origins and the Norse creation myth but I’ve always been of the belief that, that was a much later mythological creation and arguably not indicative of Norse or early Germanic belief.
All that aside I think there’s a connection between Heimdall, Ullr and Mannus that we’re missing context on, perhaps all three are the same figure.