Your mention of the twins has me thinking about attachment and bonding, and also the possible effects of the experience of sharing the womb, which would include elements of physical competition, physical accommodation, and physical cooperation. Toss in the possibility that social learning begins pre-birth in the shared womb, even though the actual infant brain does not conceptualize, and shake it up with our emerging realization of the matrix of naturenurture.
Contemplate consciousness vs. self-consciousness. Awareness vs. self-awareness.
The newborn infant definitely has what we call 'awareness', but does not have awareness that discriminates between 'self' and 'other.'
Then go read and contemplate on Eastern philosophies about consciousness and awareness, some Carl Jung, and some Joseph Campbell. Talk to some one who has had the repeated experience of dreaming about the death of family members who have then died quite unexpectedly in accidents or from things such as stroke or heart attacks where there was no prior knowledge or indication of cardiovascular problems, or from a sudden and severe illness within a few weeks of the individual having the dream.
Look at your plastic keyboard and contemplate that it is what it appears to be in terms of the limits of our senses and what they tell us about 'reality', then think about chemistry, physics, atoms, particles, string-theory, the space-time continuum, energy/matter.
Self. Other. I am me. You are you. We are separate. We are related. We are interrelated and interdependent. I can wrap my mind around those concepts. What if, in addition, we are also NOT separate but related and interdependent. What if we are also not separate at all? What if we are also, and quite literally, one?
I don't have any beliefs about that. I am simply open to the possibility.
What is objective reality? What is consciousness? What is awareness?