a question about sibling

i'm not sure if this is the right place to put this.... but i would like to hear some thoughts of people who were adopted and raised with siblings... i took my middle two daughters to get their pictures taken by a professional photographer yesterday... i have billions of prof. photo's of the oldest daughter... and then hardly any of the next two... i pointed out a display photo of two sisters who looked very much alike, and commented that i would like a photo similar of my own daughters... i told the photographer "out of all my daughters, these two look the most alike. They have the same father." i paused for just a moment... and added "and the same mother." their oldest sister is a half sister... and their youngest sister was adopted... but the middle two are full sisters. that got me started thinking.... and i spent much of my day wondering about sibling relationships.... i think for my four daughters, they view each other as sisters... period. i don't think they mentally divide each other into "full"... "half"... "adopted" they just don't think like that... they are all being raised together in the same family with the same mother and father.... and they are sisters.... but as an observer... i wondered if deeper issues exist... for example... the two full biologically related sisters... look very much alike... do they have to fight harder to establish their identity? the adopted sister does not look like any of her sisters... will that make it easier for her to establish her identity... or harder? the oldest sister has a very different personality than her two middle sisters.... does she feel "different"? do the two middle sisters who are similar have to struggle to differentiate themselves from each other? will the adopted sister and the half sister feel like they are missing something because they do not have a full sister? do the two full sisters have something "special" because they have each other? because they are being raised by both their parents? will the youngest sister who was adopted at birth feel like she is missing something because she is not biologically related to either parent? these are only some of the questions floating around in my brain.... i hesitate to think it just doesn't matter.... because i think on some level, it will affect all of four them as they are growing in ways that they may never fully comprehend or understand... sister relationships are complicated in biological families... and i just wonder how these differences will manifest themselves in my daughters lives.... and if there is anything a parent can do to help those manifestations be positive..