You didn't state if you were trying domestic adoption or not but I'll give you my input on domestic adoption and prior children, as that's where my experience lies. I'm sure others can give you other information as they all have much experience.
I placed my birthdaughter with a family that had three (older) boys from the Adoptive Dad's previous marriage. Some of my friends and family were confused as to my reasoning, and here is
my own personal reasoning which is in no way the reasoning or thought process of every potential birthmother or birthmother out there.
I wanted my child to have siblings. I also knew, from listening to stories during our match conversation and following ones, that they knew how to parent children. I knew that even the most stubborn child (if she caught my gene) would be fine in their home.
I
only looked at families that had other children and it did not matter whether they were biological or previously adopted. (And it didn't matter to me in my heart OR mind; all children are equal.)
I know other birthmothers have thought about the situation differently but I just wanted to give you hope that there might be others who think like me.
I hope you are matched soon enough. *hugs*