Citizenship Guatemala and/or Cuba

A question about citizenship in Guatemala, and potentially Cuba.

My father was born in Cuba in 1954, but the whole family left when he was a little over one year old. They lived about 15 years in Guatemala and eventually landed in the US. He married an American, had kids and the rest is history. But I wondered if my father qualifies for Cuban or Guatemalan citizenship, and also if his children would. He still has all the documents and everything but doesn’t care about that stuff anymore. I’m a bit more curious.

According to this, if he was born in Cuba he had Cuban citizenship from birth. However, since Cuba does not recognize dual citizenship if he became a naturalized US citizen he has lost his Cuban citizenship.

To acquire Guatemalan citizenship, he (or I suppose his parents) would have had to renounce Cuban citizenship, and I assume take other formal steps to be naturalized. So if he were a Guatemalan citizen he would probably know it.