Brothers with Down Syndrome.

[FlawlessHappiness]

How do you define serious symptoms?

Yes, you're definitely able to tell that they have downs.

Neither of them speak clearly, but they both do speak.
One of them speaks all the time while the other doesn't (Though he do know how to. He just doesn't want to).
They don't learn as fast as everyone else, therefore they go to a special school for kids with downs.

Something you almost always will be able to tell from a downs is the placement of their eyes and their tongue. The tongue is usually pretty large and the eyes are small.

What were you thinking about more specifically?