It is not. Forwarding a ticket always results in a new ticket for the person forwarding the email.
What you can do is open the ticket email in your mail client and drag and drop the email from your main inbox to the ticket inbox. This may or may not result in a new ticket depending on email header information (that is generally hidden to the end user).
If I think that an email is going to result in a second ticket I will hit reply and copy and past the email headers and message into the ticket as a response.
