Can a play be part of two game groups?

Can a play be part of two game groups? If not then can I filter a game group to only show certain users? I have just imported all of my plays using the bgstats app but in reality only 6 or 7 of the players are actually part of my 'game group' and would be interested in the stats between each other and to not have a 'nemesis' who isn't part of the group.