Complex sentence: She had at least four illegitimate daughters by Alexander; three of them (two named Yelizaveta and Zinaida) died in infancy, and the other, Sofia, lived to aged 16.
Split into simpler sentences: She had at least four illegitimate daughters by Alexander. Three of them (two named Yelizaveta and one named Zinaida) died in infancy, and the other, Sofia, lived to aged 16.