the later two had countries who already saw themselves as closely related if not the same culture under different states
To a certain extent, but the German Catholic kingdoms did not want to unify with the North German Federation due to Prussia. So having a southern German confederation for example is quite possible. Or even not have a unification depending on how the cards are played. The biggest factor in German unification was Bismark, without him Prussia will not have the necessary tact to navigate European diplomacy with such mastery. The north and south of Italy were very different, and one of if not the most important insurer of Italian unification was Napoleon II.