Sorry that I can't help with this. I don't have any data or knowledge of the individuals you noted. It may well be that you do indeed have an ALANSON or ALLANSON lurking in the shadows awaiting discovery. That would be a logical reason for the name appearing as a given name in your family.
I think we might have communicated earlier. Sorry if I'm confused. There was an Illinois line of Allanson, but apparently no kinship to my own family, unless an ancient one across the pond and out of known history.