Looking at the wiki page on this group, it says that the Knights of Ren consist of Snoke (the leader), Kylo Ren (one of the knights), and six others. Are there any clues or canon details that indicate who the other six people are?
We now have a great deal of information about the Knights of Ren including their identities (Ap'lek, Cardo, Kuruk, Trudgen, Ushar and Vicrul), that their order was originally founded by a man named Ren, that they're all mildly Force sensitive and that they report to Kylo Ren (but ultimately to Snoke/Palpatine).
An enclave of masked warriors wielding distinct weapons for ranged and closequarter combat, the Knights of Ren are elite, fearsome enforcers of Kylo Ren's dark will.
As of 1st April May June July 2016, we have no information about the identities of the Knights of Ren nor any information about their backgrounds or histories.