I don't think so - the Perkins is designed in UK but initially built in Japan but now built in UK I've been told; Kubota is a small Japanese company making predominantly small industrial diesels(Nanni & Beta use these base engines); Yanmar make their own marine diesel; Mitsubishi again make their own; Isuzu I don't know about.
Bearing in mind they are all indirect injection units, they will all look similar in design bearing in mind the gradual advances made over the years. I'm sure they all take their competitors engines to pieces and copy all the best bits - that certainly what I did years ago when building industrial equipment. Also a lot of the ancillary bits - water pumps; alternators, heat exchangers, fuel pumps, fuel injection pumps all come from the same outside suppliers.
So all in all, not surprising they all look similar.