Games with a ball, large or small. Games with marbles. Games with a rope. Are the cousins boys or girls? Old-fashioned games like jacks, dolls, and hopscotch cross language barriers.
I’d have to guess that there are not too many things that kids with that age range could play together, language barrier or no. How about finding something they do all play and then joining in?
Hangman is a word game. You have to be well matched in a common language to play it. It would not be recommended for people who use two different writing systems.