I've namechanged.
All my life I have struggled in groups of 3 and am always the one left out. Always. If I'm talking to a friend at the school gates and someone comes along that they know and I don't, they start talking and I am left out. If someone I know comes along, I can guarantee they will come over to talk to me but will end up talking to the person I was originally talking to even if they don't know them.
I used to go to Zumba one night a week with two others and stopped going because I got left out. If I meet 2 other friends at say a soft play place, I will get left out.
What is the secret to not being left out? Should I immediately pounce on the person that comes over and start asking them questions and not give them a chance to talk to the other person? Walk off if a situation becomes about three rather than two and just avoid situations like that? I really need some help and advice.