Strategic News Global Report tells us that the 20 people mentioned in the 2016 NIA chargesheet were very interconnected with each other when it comes to radicalization. 17 of them came from a single district. From Kasaragod district in Kerala. A 2020 report from the Hindustan Times stated that some more people joined later so in total, there were 22 people from Kasaragod.
This article in India Today from 2016 states that the trend shows that not only single youths are joining ISIS, but the whole family including husband, wife, and even the children have gone and joined ISIS.
It is also mentioned in the article that most of the ISIS recruits before this were from Maharashtra, Karnataka and Telangana. Not from Kerala. But this Strat News Global Report goes on to say that by 2018, 60 Indians had travelled to Afghanistan. Of which 26 were males, 13 women and 21 children.