Difference between ctrl-z and in linux

Question

My understanding is that when you are running any command within a given shell (say bash), what's happening under the hood is that a fork system call is called, and sleep 10 is now running as a child process with the parent being the bash shell I executed the sleep.

Now, if I want to send sleep to the background, I would either do sleep 10 & or run sleep 10 and press ctrl+z so the process is sent to the background. pstree shows that using any of these options, sleep keeps being a child process of the bash shell.

Now my question is, when doing this through SSH, I noted the following: If I do: sleep 999 & and sleep 888 <- followed by a ctrl+z, and the close the ssh session, only sleep 999 & survived.

Why is this? I actually was expecting one of these:

• both processes get terminated because the parent process is gone

• both processes get associated to init as the parent process.