Wait until your baby sits independently with a steady head, usually by age one....

https://victor-wiki.win/index.php/How_Do_I_Brake_Smoothly_With_a_Kid_in_a_Rear_Seat%3F

Wait until your baby sits independently with a steady head, usually by age one. Choose front mounts for interaction, rear seats for stability, or trailers for reclining safety. Always confirm neck strength first. Helmets are non-negotiable every ride!