I can understand, but:
1) they are indeed two dragons, but of opposite inspirations. They don't look alike at all;
2) I think Kaido and Loki have in fact opposite elemental powers too, which take them even more apart.
Kaido had Fire and Wind; Loki has lightning and ice. He may even have soul powers, which could give Loki a completely different set of Powers in fact.
Maybe we'll see Fenrir for Hajurdin.