The 'sshd' process on the target Linux apparently forks a process to handle each connection . . . with two SSH sessions the Linux target looks like this (pstree -p):

        |-sshd(1017)-+-sshd(5495)---sshd(5561)---bash(5562)
        |            `-sshd(5595)---sshd(5631)---bash(5632)

When the ssh sessions die, only process 1017 is left.