Car manufacturers' interconnecion is amazing by itself. Direct "competitors" share engines, gear boxes [1], or the whole vehicle [2] (modifying just interior and badges, of course). Seems like they adopt the same strategy as laptop manufacturers did (though likely the other way around) - cheap and middle range cars are OEM ones, especially commercial vehicules (made under someone's license with minimum modifications), while only high-end are independently developed.

1. Aisin owned by Toyota provides gearboxes to VW, Skoda, GM, Nissan, et al: https://en.m.wikipedia.org/wiki/List_of_Aisin_transmissions

2. Same car, different badges: https://en.m.wikipedia.org/w/index.php?title=Renault_Trafic&... (see "Also called")