My adult son cannot complete his studies and lives withus .he is 28 amd blames us for all his failure .Very unhappy and threatens suicide very often .Has very few friends .loves listening to music but refuses to do anything with us parents,
Please advise

Why can't he complete his studies? Is he mentally challenged? Has he ever had household chores to do? Has he ever had a job and earned a paycheck? Please tell us more.

Technically.. he became an adult when he turned 18. And generally you were under no further obligation to support him. (if he's mentally challenged that can change things).

I'd start by REQUIRING him to get a job, pay you rent (even if you put it into an account you plan to give him at some point when he starts acting his age).

I'd also require him to follow house rules you set and require him to do a given set of chores.

If he failed to do any of them you are within your right to evict him from your home. It IS YOUR home... he is only a resident there. And can be evicted just like any renter would be.

Why would his parents allow this behavior?