Whether accepted task will be visible to visible to other members of the group inbox.

Just to be sure, you are talking about tasks on Tempo or tasks via task report?
I think it should not be visible and even if it is, you will not be able to do anything on that task. 

Thanks Harshit for you response, here in my case accepted task is visible to other members. How can I remove this task from other user inbox?

Is it in Tempo or on your customized site?

I guess, you are using the Task Report. You need to add a additional filter, check either accepted by column is empty or accepted by equals loggedIn user

Hi, Yes the task will be visible if you are using the task report when you open the task info box will appear on the top and if the reassignment option is enabled you can reassign it to yourself and work on that task. 

Hi Adiyag 

1) I couldn't find  accepted by column, whether you are mentioning tp!owner.

2) How you will set this condition accepted by = loggedIn user.

Thanks.

Correct. In the queryProcessAnalytics, you can just add another filter where tp!owner = loggedInUser(). 
Make sure to add this field (tp!owner) in the report and then filter on it. 

Thank Harshit, issue resolved.