There are some threads around with this question.
Your correct people are not blood hounds. If you and your brother were Siamese twins it would be difficult to know who the signal was coming from but most likely you wont be glued to each other all night. Generally with those close to us it takes repeated exposure before the react anyways because they have preconceived notions about us. By the end of the evening they would know where the vibe was coming from they just would not be conscious of it.
Some vibes may take a little more time to process in certain environments but we process them and determine where they come from in the subconscious. Science cant totally explain how our senses do what they do. They just do it and our brains process it
Think of it this way. Suppose two people, sitting next to each other said the exact same thing at the exact same time. How do you know whose voice is whose ? You just know from the pitch, direction, tone and other factors even though these signals are coming just fractions of a inch apart your brain has the ability to determine its source and separate them.
Suppose you turn on a light in the room. Everybody in the room benefits from the light but that doesn’t mean you cant determine the source of the light.
This is not to say that mistakes dont happen but most of the time its easy to pin point the source of what is stimulating our senses.
When your out in a crowd there are times when those around you benefit from your pheromone signature but this occurs with your natural one as well. This is where the other senses, body language, social skills and congruence kicks in which is something else we talk about. Pheromones are not magic they are one small part of the big picture of communication and attraction.
They help you reach a goal but they wont do all the work for you. In some situations like sitting at the dinner table with your brother it may take a little longer the “instant” to process. He may benefit from your signature but just because he is benefiting doesn’t mean you will stop benefiting from it.
This link will shed some understanding on how our senses work. http://www.hhmi.org/senses/d110.html Pheromones are not a perfect science and there are a lot of unanswered questions that are still being explored. Be sure to check out the other links on that page they are very interesting.
Tisha