Trying out ansible's group-of-groups behavior, where the top-level group also includes hosts. Targeting groups B &C do *not* include the parent and chidlren; targetting group A appears to get all hosts correctly.

inventory.ini

[groupA]
containerA ansible_host=10.3.114
groupB
groupC

[groupB]
containerB ansible_host=10.3.45

[groupC]
containerC ansible_host=10.0.3.60

lxc-ls.txt

NAME        STATE    IPV4        IPV6  AUTOSTART
------------------------------------------------
containerA  RUNNING  10.0.3.114  -     NO
containerB  RUNNING  10.0.3.45   -     NO
containerC  RUNNING  10.0.3.60   -     NO

running-ansible-output.txt

root@nrb-ord-aio:~# ansible -m ping -i inventory groupA
containerC | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.0.3.60 port 22: Connection refused\r\n",
    "unreachable": true
}
containerA | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.3.114 port 22: Connection timed out\r\n",
    "unreachable": true
}
containerB | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.3.45 port 22: Connection timed out\r\n",
    "unreachable": true
}
root@nrb-ord-aio:~# ansible -m ping -i inventory groupC
containerC | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.0.3.60 port 22: Connection refused\r\n",
    "unreachable": true
}
root@nrb-ord-aio:~# ansible -m ping -i inventory groupB
containerB | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.3.45 port 22: Connection timed out\r\n",
    "unreachable": true
}
root@nrb-ord-aio:~# ansible -m ping -i inventory containerA
containerA | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.3.114 port 22: Connection timed out\r\n",
    "unreachable": true
}
root@nrb-ord-aio:~# ansible -m ping -i inventory containerC
containerC | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.0.3.60 port 22: Connection refused\r\n",
    "unreachable": true
}
root@nrb-ord-aio:~# ansible -m ping -i inventory containerB
containerB | UNREACHABLE! => {
    "changed": false,
    "msg": "Failed to connect to the host via ssh: ssh: connect to host 10.3.45 port 22: Connection timed out\r\n",
    "unreachable": true
}