ssh -i /home/some_user/PEM_Keys/key.pem aaa@127.0.0.0

ssh -i /home/some_user/PEM_Keys/key.pem bbb@127.0.0.0

mkdir /home/bbb/.ssh
mkdir /home/bbb/.ssh/authorized_keys
sudo chown -R "bbb:bbb" /home/bbb/.ssh
sudo chmod 0700 /home/bbb/.ssh
sudo chmod 0600 /home/bbb/.ssh/authorized_keys
sudo cp /home/aaa/.ssh/authorized_keys /home/bbb/.ssh/authorized_keys