Is it contaigious, I mean hereditary?

I use to look at my daughter differently. I would smile at little oddities. I would laugh at the way she seemed to talk to her hands in the car. Once her hands got in a fight and wouldn't speak to each other....or her, for the rest of the day. She was two. Then she got into school and announced to the whole class that we celebrate Kwanza instead of Christmas. The teacher told me she could not wait to meet my African American husband.....(I had to set the record straight before she met my very non African American husband and was disapointed)
Then when trying to learn cursive she told the teacher she preferred to write in Japanese. These things were funny and quirky and cute with my first born, my daughter, my love.
So what changed when my son did the same odd things? Why was it no longer funny? Why did he end up with a diagnosis? They say more boys are diagnosed with ASD than girls. Interesting. After my son was found to be on the spectrum, I did take another look at my daughter. Wow. Did she always panic when people tried to hug her? Yes, now that I think about it she has always done that... Well, look at the way she is talking to that other kid! She isn't even looking at them! She is looking at their shoes! Does she look at people when she talks to them? Nope....has she ever? Well I can't remember.....
     So what does all of this mean? Heck if I know. I know that there are other people in our family that are on the spectrum. My kids have cousins that have been diagnosed with ASD. I just wonder are we diagnosing more kids because we know what to look for now?
I think back to my days in school  and I can think of several kids that would have been labeled aspergers. It all makes sense now that I have a son on the spectrum. Back then, back in the stone age when no one had heard of this, I went to a Jr. Prom with a guy that had aspergers. I know that now. I didn't at the time. No one knew what his deal was. He was hysterical. He had a friend drive us, we ate at a Burger King where his friend put table cloth and candles out for us....now that I think about it, his friend was a year older than us and he stayed with us the whole time. He was a good friend to this guy. He knew. No one else figured it out. That was the best prom I went to.
     We will continue to learn more about autism spectrum disorder as more and more kids are diagnosed. Maybe someday they will figure it out. Maybe they wont. I think there are a lot of really great scientists and doctors and other important people who fall on the spectrum. Do we need to "cure" this disorder? My son said he doesn't want to be any different. He doesn't want to be a loud and rowdy boy. I guess for him being on the spectrum makes him polite and calm.

   I do want to know if this is a family thing. I want to know who to thank.