I am using SPContext.Current.Web.ParentWeb and I want to know if I have to dispose below:
According to the Bible of SharePoint
IDisposable objects, Best Practices: Using Disposable Windows SharePoint Services Objects:
An earlier version of this article recommended that the calling application should dispose of the SPWeb.ParentWeb. This is no longer the official guidance. The dispose cleanup is handled automatically by the SharePoint framework.
So, no, you do not need to dispose of this object.