How do you tell someone that you did not pick them to be in your bridal party?

I have a group of four girlfriends. There are Two I am closer to and have asked them to be bridesmaids. How do I tell the other two I didnt pick them without hurting their feelings? Is thereby different role they could play? I’m thinking of lying and saying I was going to ask all four but then I couldn’t because I had to ask my cousin and niece due to family pressure. But, I have the two since I had already asked them and couldnt take it back. Thoughts?