The minimum age of use for WhatsApp is 16 years old as some content shared may not be appropriate for children, or they have contacts (strangers) in their phone who they have never met face to face.
Please click the link below to learn more about it and recommended guidelines for your child’s use of WhatsApp below:-
https://www.thinkuknow.co.uk/globalassets/whatsappguide-for-parents.pdf