Yamamoto is the ancestor of Ciaphas CainICT is set in the Golden Age that precedes Warhammer 40,000, Ciaphas could easily be an Identical Grandson of Yamamoto. Somewhere along the line, his decendants decided the lunatic he used to serve under had the right idea and began a Blackadder style tradition of self serving cowardice, and in doing so got granted a portion of Tylor's insane luck...but also inherited Yamamoto's misfortune
The show is the future of the Universal CenturyIn episode 3 Lieutenant Makoto Yamamoto reads out Tylor's letter and clearly sates the date on which Tylor was made a captain. UC 6998. United Planets Space Force (UPSF) is a possible descendant of the Earth Federation equivalent.
Tylor is like General grant.A failure at everything in life... except the army. or in this case the navy. It's why the shows starts with him on the street I presume homeless. He's tried everything else in life and was good at none of it. So he joined the navy and found he had a knack for it...