Once the results screen loads for your search query, click on the settings button, which is the cog icon on the top right. You will then be presented with a pop-up window with two tabs. One entitled "Fields - Table view" and the other "View Preferences".
On the table tab, find "INPADOC Family Count" on the left-hand side ("Available Fields") and drag it into the list on the right-hand side ("Displayed Fields"). After this, click on the green "Submit" button to apply the changes to your view. What you should see is an extra column entitled "INPADOC Family Count".
Under that new column, click on the number adjacent to the patent you're interested in looking into and it will show you a list of all patent family members of that particular patent.