I have already bought a onepassword plan on my iphone and i have also turned on family sharing, so just wanted to give him one fresh account of his own. So how could i do the same, is it possible through family sharing ? (Share purchases)
Unfortunately it is not possible to apply an App Store purchase to multiple accounts. If you purchased an individual membership then your son will not be able to set up his own account using the same App Store purchase.
1Password does offer family memberships, which would be what you are looking for. This type of membership allows up to 5 family members on one account. You can share items within the family and the family organizer can recover family accounts if needed. You can read more about family memberships here:
Please let us know if you have any questions or if we can help in any way.