How many and how old are you own children?

Do you know much about the boys past...exposure to other children, socialization etc?

What you describe doesn't sound too concerning to me. Some kids just can't handle change and cry a lot until they are used to their new environment. If he is not used to other kids then it makes sense he cries when they are near.

How long have you had him? Is he full time? Is he eating and sleeping with you?

I usually don't take my kids outside until the new child is settled in. I try to keep their day as predictable as usual, stay in the same room and keep to a routine. I find it allows them to settle in faster. The transition involved in getting them outside can be a lot to a child that is overwhelmed.

I have transitioned 3 kids in the last 7 weeks. Oddly the one that cried non-stop and got upset about everything for a few weeks is now the most easy going child that knows all the routines and is the first to do as I say. He was hardest to get settled but is now a very loyal, happy, settled little one. The others transitioned almost without tears and are a pleasure but need more verbal commands etc. Though, they are all very young. Point being, just because this little guy is having a tough time transitioning doesn't mean he will be difficult forever.