@Wombat78, officially Croatia doesn’t grant citizenship through grandparents, just parents. However there’s sometimes exceptions made (i.e. for people that were legally raised by their Croatian grandparents abroad and I’m not sure if military service of a grandparent adds a perk) You’d have to have your parent that is that grandparent’s child apply for Croatian citizenship. When they become Cro citizens then you can apply as well without having to go through the 5 year naturalization process.