Carolyne, as you have found out the Allens were/are a very secretive family.Either they didn't like each other much, or something as no one knows anything about the family or who is or isn't related to them.
Even when they lived in the same town way back when, you still can't prove they were related to each other.
DNA testing is helping a bit.If the researchers are correct my Hiram Allen did not have any brothers, so that makes it hard to prove conclusively if the family he's been assigned to is or isn't his line.Hiram did have a bunch of sons, but over half of them, their names are not known.My great grandpa only had daughters.
There is a King in my line who married an Allen descendant, Henry King b. 1792 married Abi Eiland, she was married to John Gibbs Hitchcock before she married Henry King.
Some of the counties associated with them were Macon, Al, Barbour, AL, Madison Co., AL, Russell Co., AL and Jones Co. GA.
Abi's parents were Judge Stephen Eiland and Mary Allen. Abi and Henry King had two children I'm aware of, Nancy Miriam King and Lewis Hillard King.