Amazon AWS Account Sharing with iOS

I am considering using Amazon AWS for the 1st time, so I am trying to get familiar with its capabilities. I've been reading through the AWS documentation for S3 and Cognito, but I'm not sure if AWS will support what I need, so I'd like to know if anyone who has experience with AWS can shed some light.

I have a client who has the following request for an iOS app that allows users to essentially upload and download files:

1. An end user can create an account (I assume using AWS Cognito) where he can upload/download files (AWS S3) that other people can't access by default

2. This end user can provide access to his account to friends, giving friends the ability to also upload and download files within the created account. The original end user has the ability to delete files (he has total control), but not his friends (friends can only upload and download). I'm not sure if AWS Cognito supports this shared account ability.

Is the above scenario possible using AWS, and if so, how straight-forward would it be to implement? If the requirement was only for the original end user to access the account, then I know from the documentation that this should be straight forward. But, with the added requirement of delegating access to friends, I can't tell from the documentation if AWS supports this, and if it does support it, how easily does it support this feature.