Mr McDuck was an anthropomorphic duck.
This man, by all appearances a naval officer of some sort, was one of Scrooge McDuck's ancestors. Though he was at any rate related to Seafoam McDuck, it is unclear if he was Seafoam's son (and therefore Scrooge's great-great-great-uncle), or Seafoam's father (and therefore Scrooge's great-great-great-grandfather).
Behind the scenesEdit
However, due to the erroneous translations of the Carl Barks stories on which Grote based his efforts, Seafoam McDuck was there depicted as Scrooge McDuck's great-great-great-great-grandfather, while an anonymous character, Seafoam's grandson, became Scrooge's great-great-grandfather. As such, where the duck this page covers falls in the genealogy if one puts Seafoam back in his proper place is up to interpretation; one may wish to preserve his relation to Scrooge, and thus make him Seafoam's father; or one may favor preserving his intended relation to Seafoam, keeping him as Seafoam's son but consequently making him Scrooge's great-great-great-uncle.