become: ansible_os_family == 'Darwin'
become: (ansible_os_family == 'Darwin')
become: {{ ansible_os_family }} == 'Darwin'
become: {{ ansible_os_family == 'Darwin' }}

- name: Become need
  command:
  become: yes
  when: ansible_os_family == 'Darwin'

- name: No become need
  command:
  when: ansible_os_family != 'Darwin'

[Darwin]
server1
server2
server3

[Darwin:vars]
ansible_become=true