I said up thread...
You are right, you do need to consider the impact of adoption on birth children in a way you do not with another birth child because there are more uncertainties with looked after children. I can say more if you like.
Someone has asked me to expand, so I know Lilka and others can add a lot more here, Kristina if you are looking in, devora, Kew and co??
Basically, all/almost all children who come through the care 'looked after' system have been affected by a combination of things, the loss of birth parents, and probably the loss of foster carers (maybe multiple sets of foster carers). Also there may well have been issues in the birth family such as drug or alcohol abuse, mental health issues or learning difficulties. In some cases there may have been drug and alcohol abuse and mental heath issues etc, or learning difficulties and associating with 'risky' people such as drug or alcohol abuses with the result that birth parent/s could not keep the child safe. Children might have had al manner of neglect or abuse. This all leads to a possibility of a child who is affected by these experiences and may almost certainly have issues related to these things either from their genes or from their environment or both.
Having said this the children are just children and having a birth child who is pretty emotional and a bit of a handful at times I know that genes and experiences are not the full story. Children can be amazing and even after a tough start in life can go on to live brilliant and vibrant lives with the right parents.
For me, I really wanted to parent another child, wanted my birth child to have a sibling and had wanted to adopt for the past 20 years. So it was pretty much a no-brainer BUT I needed to be really ready for it! DH was ready long before me. I wanted IVF with donor eggs before I would give up on another birth child and after two cycles and a frozen cycle of IVF (with donor eggs) which all failed, I felt I was ready to say goodbye to IVF. Once I had closed the door on IVF I felt ready to embrace adoption. Now I could not imagine it any other way and after less then a month I would not swap ds for another birth child.
I was very cautious about the kind of child I could parent, I am older, late 40s and I have limited energy and so I knew I could not handle a child who was really full on or really ill with a life threatening disease/illness. That is just me. I had my things on my list I was worried about but ultimately, when I read little ones profile - DH and I just felt he was right. He kicked lots of our boxes but not all of them, it was funny, he was not what we were expecting but now he seems the absolute right fit for our family!
He has just come down to give me a goodnight kiss (I wrote this out a little while ago!) and is utterly adorable.
Of course there may be problems down the line and I must be ready for them, that is what I have signed up for! DH and I. Love makes it all easier but I know from others love does not always come quickly or easily. So all in all I think it is 50% head (working out what is best for your family, what you can handle etc etc) and 50% heart, just that feeling that this is right.
Whatever you are feeling about the process go slowly, read lots (I read on the Internet and not books as dyslexia is a problem for me with books!) and talk to people and get info and ultimately it must be your choice for your family.
My DD was fully on board but ultimately we as parents had to make that choice for the whole family.
Good luck one and all.