How DS1 views adoption

On the play ground shortly after we returned from China, I meet one of DS1's friend's older sister. She's 7. She didn't believe DS1 had a brother and came to check him out for herself after DS1 had told her he was there.

She informed me, "He's adopted, his face is not like yours". I said "yes, he is adopted, he is DS1's brother and we all have different faces." She was cool with that. DS1 was happy with that response. However, this made me think that while I had told DS1 we were adopting, I wasn't sure I had told him that he himself was not, and the "blended family" approach is something I might need to give him ammunition on. But what do you tell a 3, almost 4 year old?

So, we had a talk. I only wanted to explain basics and not give more information as necessary. But I also want him to have the ammunition necessary to explain things to friends or on the playground. I told him he grew in my belly. That all babies grow in some one's belly, specifically women's, bellies. That DS2 grew in his mommie's belly in China. However she wasn't able to take care of DS2 and asked us to help out. We did so, because we wanted another child in the family. Now he is my son, his brother. That they happen to came from different women's belly's, but that we were a family now. He had no questions. He just wanted to know who else we were going to play with that afternoon.

A week later we went to a karate introductory class, without DS2. We were a bit early, and the teacher was trying to make small talk with him, which if you have ever tried to make small talk with a 3 year old, is an interesting task. He asked DS1, "what did you do this summer? "
"I got a new brother."
"Did the stork bring him?" the teacher asked.
"We got him in China" stated matter of factly.
"Wow."
"I'm from China too!" says my blond-haired blue-eyed son.
"Really?"
"Yes, but I came first!"

Given he's starting preschool, I'm sure more questions are to come. I'm trying to bring it up once a week or so, just to see if there are any questions.

Sunday night he surprised me and asked me why DS2 blows his nose a lot. I hadn't expected to discuss cleft lip/palate this early, but I jumped in. I reminded him that DS2's mommie in China need help taking care of him and one of the reasons was that DS2 had a hole between his mouth and nose. That made it hard for him to eat. I further explained that most of the hole has been fixed. However, DS2 blows his nose sometimes because there is still a little hole in there and he is cleaning it. Going for the boy approach, I explained that if we feed DS2 spaghetti bolognese, we might get some red sauce out his nose. This lead to an interesting discussion of the rest of bath time talking about different foods we could give DS2 to make different colors. Of course, DS2 was there for the whole discussion and didn't seem to mind.