The phrase "same nationality" means that two or more people come from the same country or belong to the same nation. It highlights their shared citizenship or ethnic background. Full definition
on certain players attracting players of same nationality... «No, most of the time it is the players who want to join you who come in. (justarsenal.com)
The Muslim aristocracy was feudal in character, depending on levies enlisted from the middle and lower classes of Muslims, usually of the same nationality as the feudal leader. (religion-online.org)