User who asked the question has user id 319426 and the user who responded to the question has user id 325733 (this link no longer exists because the accounts have been merged). There is no restriction (uniqueness) forced in user names. Multiple users can have the same name Jim Bob.
Those two accounts may or may not be the same person.
In this question, the OP name is Siva and I posted an answer to the question. However, I didn't ask the question.
The same gravatar image in your question leads me to believe that the same person created both the user accounts.