I really feel for kids with developmental disorders, such as autism.  I have a relative who has it
That's too bad!  There are so  many different kinds of developmental disorders - language disorders, learning disorders, motor disorders as well as autism. It's really sad!
Yes, and I found that autism is 4 or 5 times more likely to occur in boys than girls
Yes, and it's typically noticed in the first two or three years of the child's life.
And it is reported that it effects over 24 million people across the world
Genetics is a strong component in developmental disorders.
Yes it is.  It has also been theorized that things such as vaccines and drugs use during pregnancy can influence it 
I've heard that.  There are a lot of controversies surrounding  proposed environmental causes