The following diagram from APUE leads me to wonder if a a session leader the only process in its group.

The hangup signal is sent to the session leader, while other signals are sent to all the processes in the foreground groups. If the session leader is the only process in its group, then the two cases seem to be more consistent with each other.

Is the session leader the only process in its group?

[![enter image description here][1]][1]


 [1]: https://i.sstatic.net/cFdSu.png