Hi and welcome to the forum!
Bengals can be very precious about their litter box! Mine also like one for poo and one for wee. One Bengal is less fussy than the other though. Jagger will not use a tray if it has been used at all without being scooped out first. But I wouldn't want to use a toilet if it had been used and not flushed so I kind of get that
I also had to change the type of litter and location for him. These are all things you need to look at - where you want the litter box may not be where he would like it positioned!
Sometimes, if I can see he needs the tray but won't get in it (he will get in and out and get agitated), then if it is clean, I just put some fresh litter on top and then he will use it.
Are you absolutely certain the other cats don't use the litter trays at all? That could also upset him if he considers the trays his as he is the only indoor cat. Jagger will guard the one we now have in the hall from Hendrix if he thinks he is going to use it. If the weather is bad, both of mine will use their trays if they don't fancy going out.
Stress is something you need to consider as well. How is the relationship between your cats? Stress can be difficult to work out, so you need to watch them all very carefully and how they interact. Have a read of Cat v Cat by Pam Johnson-Bennett - its a must have for multi cat households.
Litter box etiquette is a minefield!! Good luck!