I am the oldest of 4, and I am the typical oldest child. I am always the responsible one. My hubby is the younger child of 2, and his personality fits with the second child as he is very laid back and gets along with everyone.
Our son(almost 4 years old) was only placed with us 2 months ago, and is our first child, as well as he was the first child by his birthmom too - however right now he has a lot of characteristics of being the baby of a large family and I think the reason for that is that for the past 2 and a half years he has been in foster care with a family that had three girls that are all preteens - so old enough to really baby him
It will be interesting to see if over time he takes on traits of the older child, since that was originally is place by birth and will be here too as we are pretty certain that are family is still going to grow.