Hi ChoudeBruxelles I would like to wish you well on your journey.
We too have a birth child, a DD aged 8.
We are on the adoption journey, just at the start of home study.
I loved our hamster and he was in no way related to me, I love my friends kids and they are not related to me, I had treatment with donor eggs and had that been successful the baby would not have been genetically related to me. They are all bits along the journey (yes hamster is flippant, not meaning to cause offense but I did really love it and DD and I wept buckets when it died this year). The thing is, if someone were to come to and say that there was a mix up at the hospital 8 years ago and DD was not my birth child, would love her any less, and I know I would not. They are all little things that make me think (not know because we are not there yet!) that I will be able to love an adopted child as much as I love a birth child.
They will look different, they may have different mannerisms etc but I do think that a lifetime of experiences and a comittment to love and care will make up for those differences. Also, birth children are only 50% our own DNA (or whatever the maths is) the other half is my other half who looks different from me, acts different from me etc etc. My mum was my biological genetic mum but we look different and act different etc. So sometimes I think biology/genetics is so much only a part of the story.
Thinking all that through has helped me to be a tiny bit prepared but long term I am not sure how it will all pan out. I just know the closer I get to it (the adoption) the more positive and the less concerned I am about stuff like birth verses non-birth... for me there are lots of other issues like what type of child could I parent etc, etc, so I am in no way making light of the enormity of it. Our DD is very positive about it all but we have been lucky in that she is pretty open and luckily she is not too hung up on it all happening soon.
Good luck.