Is it common for young adults say (24-25) to use the term この子 for a younger adult (20-21)

[GenkaiPower]

I wonder as I was reading a manga where a character whose 24/25 use the plural of kono ko to refer to 15 year old and someone whose age is not state but I believe to be 20-21, and is this a normal usage

 

[mdchachi]

I wonder as I was reading a manga where a character whose 24/25 use the plural of kono ko to refer to 15 year old and someone whose age is not state but I believe to be 20-21, and is this a normal usage

Yes