Croats are southern slavs, they're like us serbs and we're like them. Divided during the schism between the western/eastern church. Until like 1100's we helped each other out many times + fought (wouldn't be slavic if you couldn't unite hehe)
I don't want to stir arguments here, but I have to say that Croats are not like Serbs, and Serbs are not like Croats. There is nothing bad about that. I really don't understand why are Serbs constantly telling us what we are and what we aren't.
Back on topic. I can only say that from what I have seen light eyes and light hair is pretty common among Croats.
I had 19 classmates in my highschool and 13 of them had light eyes (including me) if I remember correctly 5 of them had blond hair and others had light to medium brown hair. On my college light eyes and hair are common too.