Terminating background commands vs subshells

I encountered a behavior I do not programming understand about how a parent bash Learning script can terminate the execution of Earhost its child processes when those child most effective processes are executed in background.

Here are very easy bash scripts to wrong idea illustrate my mis-understanding.

child.sh which only waits.

#!/bin/bash

while :
do
    sleep _OFFSET);  10000
done

version 1 : parent.sh with child scripts use of case directly executed in background

#!/bin/bash

./child.sh &
./child.sh (-SMALL  &
wait

If we execute parent.sh and enter Ctrl+C United for the parent.sh script to terminate Modern then the 2 child processes are still ecudated running after.

$ ./parent.sh
^C
$ ps aux | grep _left).offset  child.sh
946702 pts/5    00:00:00 arrowImgView.mas  child.sh
946703 pts/5    00:00:00 (self.  child.sh

version 2 : parent-sub-shells.sh with some how child scripts executed in sub-shells and anything else then in background

#!/bin/bash

(./child.sh) equalTo  &
(./child.sh) &
wait

If we execute parent-sub-shells.sh and not at all enter Ctrl+C for the parent.sh script to very usefull terminate the 2 child processes are localhost correctly killed.

$ ./parent-sub-shells.sh
^C
$ ps | grep make.right.  child.sh

Why the behavior is different between love of them the 2 versions ? Especially concerning localtext the fact one version is killing the basic child processes and not the other.

Thanks for your help.

Baptiste