I have a friend (grew up with her so have seen how hard it's been) with an older brother with DS.
He is not the happy, smiley, "can do anything he sets his mind too" idea that is often portrayed of those with DS.
He has multiple health problems, is non communicative and extremely aggressive and has been physically aggressive.
She has grown up always coming second, to being alone in her bedroom (because it was easier to keep her away from him then him away from her) for hours, to never being allowed friends around, to constantly being unable to go out i case she was needed when he had an outburst, she's been hurt by him, ignored, seen her parents desperate and pleading for help from people and authorities and no one has helped, at 28 she still lives at home because her parents are now in their 60s and are struggling
she would desperately love her own children but is too scared to risk having a child with DS and she knows that at some point, she will become his carer and doesn't want to subject her children to the same experiences she had growing up.
Her parents are wonderful, kind, generous people but they are broken ,they are desperate and they are so sad. They are not in great health themselves and spend every day terrified of what will happen to him when they die, each scared they will die first leaving the other to cope on their own.
They both agree they if this test was available 30y ago, they would've terminated the pregnancy and even more now they know what they know
They love him, he is they're son but This is no way for people to live