Grid tickets are bound to accounts. This means that if you buy tickets for others under your account, they are bound to you. That's why they all have your QR code.
Tickets can also only be used with the Grid App. Screenshots or similar will not work.
In order for friends to have their own ticket, they must set up their own grid account and buy their tickets themselves.
If you have tickets for your friends in your app, the easiest way is to come to the event together. You will then be admitted together.
The same applies to group tickets. Here the group is asked to come together.