I get questions from time to time where people say they cannot add/ remove users to/from certain groups even though they have full control on the site. Matter of fact when they open the group (to add user to the group) the site owner is missing the ‘Add Users’ submenu (as shown on the figure 1). The solution is pretty simply but let’s give you the scenario first how people may get into this situation - so that everyone is on the same page J

Scenario:

IT created a new SharePoint subsite for you and created few groups for you and given you full control on that site. Now you took the site over and happily started laying your contents but just when you thought to permission your colleagues contributor rights adding to the ‘Members’ group (which was prepopulated by your IT peer) – you realize you don’t have the ‘add user’ menu item.   

If you ever run into this situation – here is what happened: IT colleague when created the contributor group forgot to change the group ownership. When you create a new group SharePoint automatically makes you the owner (the Owner field is being populated by the account you signed in with – see figure 2 below).  Unless you specifically chose someone else to be the owner (another group can be the owner too). So basically you are missing the administration rights for that particular group

Solution:

Now that we know what happened - how do you fix this? Either the group owner (or someone with administration rights usually the IT folks) can make this amend navigating to the http://YourSiteUrl/_layouts/15/groups.aspx page and change the group ownership (editing the group). Also you can click the group to open > Settings > Group Settings > Group Owner.

In our previous Members group example you will typically make the ‘Owners’ group the 'Group Owner' of the 'Members' group. This way you being part of the Owners group will have full rights on the Members group (and get ‘Add Users’ submenu). Once this is done don’t forget to refresh your page though
J

I hope this helps someone and save some headache.  I’d love to hear your feedback.

    
 Figure 1: Site owner missing 'Add Users' submenu  Figure 2: Change group ownership