His father was Pepin the Short, the Frankish leader. Do you think he was short? He definitely was very short! Pepin became the king of the Franks in the year 751 CE. In 754 Pope Stephen II unfortunately appoointed both Charlemagne and his younger brother Carloman as the next rulers of the Franks.
When Pepin died he left his empire to his two sons. Not sure this was such a good idea as they used to fight a lot! But eventually his younger brother Carloman died, and the empire was left to Charlemagne!