Claim by a non-applicant from another non-applicant in a arbitration case

There is a case before the arbitrator. There are 3 claimants and 3 non-claimants.  One of the non-claimant is colluded with the claimants. The colluded non-claimant, is his reply to the claim, has counter-claimed from the other 2 non-claimants.

1. Please, advise, can a non-claimant, in his reply to the claim,  can claim from other non-claimants? 
2. Please, advise, is  the colluded   non-claimant has any right to get any relief in his favour from the 2 other non-claimants?
3. and please, advise, should the 2 other non-claimants reply to the  colluded non-claimant's counter-claim, against them ?