Complex sentence: He was the fourth child born to the family of Ekaterina Gheladze and Vissarion Djugashvili; the prior three children of the couple had died at an early age.
Split into simpler sentences: He was the fourth child born to the family of Ekaterina Gheladze and Vissarion Djugashvili. However, the prior three children of the couple had died at an early age.