, two of them as young as two,

Those involved in choosing who was to be a successor to the throne preferred children because children could be dominated more than an adult, leaving considerable power with those who did the choosing. All Han emperors since Emperor Ming (reign 58-75) had become emperors when adolescents, two of them as young as two, and most had begun their rule with their dowager empress mother serving as regent. These women remained isolated and dependent upon men – usually their male relatives. As an emperor grew into adulthood, if he rejected his mother's relatives as advisors he usually turned to the only other males with which he had contact – the eunuchs – and he appointed them to high positions as a counter to his mother's influence.
[Return of the Han, Prosperity, and Influence by Eunuchs http://www.fsmitha.com/h1/china06.htm]

I think "as young as two" should be a complement in "two of them as young as two."
So, I'd like to know if "being" is implicit before "as young as two."
Thank you in advance for your help.