Complex sentence: Anton Baricević was born in Zagreb, Croatia, in what was then Yugoslavia, and although he claimed to be of Siberian, sometimes Italian and of extraterrestrial descent, he was most likely of Serbian origin.
Split into simpler sentences: Anton Baricević was born in Zagreb, Croatia, in the formerYugoslavia. Although he claimed to be of Siberian, sometimes Italian and of extraterrestrial descent, he was most likely of Serbian origin.