If he digitally downloaded everything on his account, then yes, you'll have to buy everything on your own to play (plus PS Plus). Reason being because his account owns the license to those games, but if you downloaded the games on your account, then you own the License and you only need to buy the membership.
Hope that helps and Good Luck Guardian :)
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Oh okay. Thanks a lot! He did digitally download Rise of Iron.
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You're welcome Bro, sorry for the late response, work and Playstation kept me busy from the forums lol.