Show CPU core usage for parent process and its child processes

the code

pgrep -P $(pgrep supervisord) | xargs ps -o %mem,%cpu,cmd -p | awk '{memory+=$1;cpu+=$2} END {print memory,cpu}'

will get only one child layer

if u want to search for all processes that were derived from a main pid, use this code ..

ps -o pid,ppid,pgid,comm,%cpu,%mem  -u {user name} | {grep PID_PRINCIPAL}

The pid of main processe is the PGID of child processes.

I don't have access to a BSD machine to check but your ps command should work as advertised. In any case, as a dirty hack, you could always just parse the output of the full ps (where NNN is the PID you are after):

ps aux | awk  -v OFS="\t" '$2=="NNN"'

Or, to keep the output format identical to that of ps:

ps aux | grep -i '^[a-z ]*NNN '

You may have to tweak the ps options a bit since they're different in BSD. Just use whichever combination prints all processes.