Found an example on the ros2 tutorials (Foxy)

https://docs.ros.org/en/foxy/How-To-Guides/Launch-file-different-formats.html

perform remap so both turtles listen to the same command topic

forward_turtlesim_commands_to_second_turtlesim_node = Node(
        package='turtlesim',
        executable='mimic',
        name='mimic',
        remappings=[
            ('/input/pose', '/turtlesim1/turtle1/pose'),
            ('/output/cmd_vel', '/turtlesim2/turtle1/cmd_vel'),
        ]
    )