Listener question : what is the other person?

I was very impacted by the webinar last night. It’s really got me thinking about what we really are. I think the idea that the self is just learnt patterns that our brain joins up and makes a person from is  fascinating. It’s like something at the very edge of my vision at the moment and if I try and look at it too much it disappears. But it’s really left me thinking - in a good way! 
It leave me wondering who I am, what I am? And in a way more importantly to me in this moment , what other people are... because if we are all one consciousness. If there is nothing differentiating me at my core to anyone else, what makes me me? Or someone I love them? Underneath all these questions I think is one most important. I have lost people I love. I have never had faith but I’ve stTted to have belief in them being here, all around - in nature, little signs. And that one day when I die I will sense them again. Not see them but be with them. But if we are all one, I can’t see how I can hold that anymore. Because there is nothing that defines them (without the body) as them is there? I kind of want there to be.