Does this bother me? No, not in the least.
Do I feel threatened? No, not in the least.
Why? Because I understand people and I understand the intricacies of social circles. I understand that it's only natural that everyone I know, will know other people.
People have social circles, plural, not singular. Most people have their cardinal circle and their secondary circle. Some have multiple offshoots of social circles outside of the secondary circle. Social circles are aware of one another, some members don't blink twice and other members are very jealous and catty when it comes to a member of their circle crossing into other circles.
Multiple circles are normal and healthy. One circle will have more significance to a person than other circles. This will be the cardinal circle.
Some people keep their secondary, tertiary, etcetera, etcetera, groups away from their cardinal group to avoid conflicts of interest. This can be a draining task. At some point one must consider cutting ties with those that can't handle the standard social circle politics. It is especially exhausting if one is the nucleus, or one of multiple people forming the nucleus, of a group.
It just plain sucks to have to hide certain friendships from certain people in order to spare their feelings.
I just turned 36; that much closer to 40. I really can't adhere to the social circle politics any longer. Let's face it, some of my friends are more enjoyable than others. I'm not hiding that fact to spare feelings any further. I just don't have the energy. There are bigger things in the world. I've got people near death around me, I have no time to waste being fake. So let's say you build a bridge and get over it. I think you've got a problem and perhaps you need to identify what that might be and cope with it and why it prevents you from expanding yourself.
I'm a social butterfly and I have many friends. Accept that. Love all of my friends, get to know them, and keep your jealousy to yourself if you want to remain in any of my circles.