As a former bike shop service writer and parent, I recommend waiting until your...

https://magic-wiki.win/index.php/How_Do_I_Know_if_My_Bike_Can_Take_a_Rear_Child_Seat%3F_A_Pro%E2%80%99s_Guide_to_Family_Cycling

As a former bike shop service writer and parent, I recommend waiting until your baby can sit upright, unsupported, with strong neck control. This milestone usually happens around one year old