Most of them are young.

他们大半是青年人。

《新英汉大辞典》

Most of them are young people.

他们当中大部分是年轻人。

youdao

Most of them are young children in Africa, South of the Sahara Desert.

大多数是非洲，撒哈拉以南的沙漠。

youdao

Terribly dynamic and largely a very young group of players who are going to be competing in the Olympics most of them for the first time,"

VOA: standard.2010.01.12

But most of them are young.

但多数学生都很年轻。

和钢琴老师 - SpeakingMax英语口语达人

But most of them are young and untrained, and still need the neighbours' armed support.

ECONOMIST: Congo

And most of them are young.

ECONOMIST: Spoilt for choice

This is frightening: a doctor at a major medical center is telling children, most of whom are too young to even think of questioning the wisdom of a doctor, that sticking them with needles will help their pain.

FORBES: Stabbing Needles Into Children To Treat Asthma: Malpractice, Or Just A Very Bad Idea?