Talking about the Father of Dragons, is there any info about Bahamut and Tiamat in Blackmoor? I know they exist since the earlier incarnations of D&D (the original Greyhawk supplement name then the Dragon King - aka Platinum Dragon - and the Dragon Queen -the Chaotic Dragon, but is obviously Tiamat).

I'm interested to know if Dave Arneson incoporated them in some form in the original depiction of Blackmoor.

My players are making their own theories, and I want to know if there is any canon information to supplement them.

Well, my players' theory is the opposite. In the second 4e Draconomicon, there is this lore about Bahamut being known as the Grandfather of Dragons because he has a son who is the true father of metallic dragonkind. This son of Bahamut has the power to kill his father and because of that Tiamat is searching for him to try to sway him to her side. The thing about Bahamut's son is that no one knows his name or whereabouts, that's why Tiamat has never been able to find him.

My players believe that, as Insellageth is the "Father of Dragons" (and a gold dragon, to boot), that means he is Bahamut's son.