The toll it takes on parents and siblings, based on stories one reads, must be horrible.

You destroy the life of the family and greatly make the lives of healthy children harder.

Why would you sacrifice your healthy children for one who has no real future?

Complete inversion of common sense.

"has no real future"?

I.e. not a net-productive member of society? Fun fact, machines are taking everything over, so you and any "healthy children" may be in that same camp very soon. IMO, anyone capable of living happily while being outcompeted by machines is well-adapted for the future.

I'm not; average Down's Syndrome folks seem to be.