Most toddlers are ready for a bike seat once they possess strong neck control...
https://wiki-mixer.win/index.php/What_Age_Is_Too_Big_for_a_Rear_Child_Bike_Seat%3F
Most toddlers are ready for a bike seat once they possess strong neck control and sit independently, usually around nine to twelve months. Front seats work perfectly for smaller kids, while rear seats provide extra stability as your child grows