This might be easily explained by the fact he married a widow, thus considering her son as his ownn
Last names did not exist at this time; the consistency checker doesn't allow for different customs in different times and places. It gets upset about patronymics, too.
Conrad II, Holy Roman Emperor is my 24th great grandfather.
Conrad II, Holy Roman Emperor is my 30th great grandfather.
Conrad II, Holy Roman Emperor seems to be my 30th great grandfather via North-West France and Sweden to Finland.
@Conrad II Holy Roman Emperor is my 28.th Great grandfather
@Conrad II, Holy Roman Emperor
is my 30th great grandfather!