Complex sentence: Proto-Mongolic, the hypothetical ancestor language of the modern Mongolic languages, is very close to the Middle Mongol language, the language spoken at the time of Genghis Khan and the Mongol Empire.
Split into simpler sentences: Proto-Mongolic is the hypothetical ancestor language of the modern Mongolic languages. It is very close to the Middle Mongol language, the language spoken at the time of Genghis Khan and the Mongol Empire.