No, you chose to have a child. With a child comes the risk of SN.
My DH is in the financial sector which involves a lot of hours at work, and I am doing some part time study until my DS is old enough to go to school, if we had a child with SN both those things would probably have to change (obviously depending on the level of SN).
I guess what I am saying (badly) is that any choice runs the risk of things not being as planned. That includes marriage, having children, basically any involvement at all!
My DH and I were discussing our wills, and we have to decide who would look after DS if we were both to die. This is an awful decision for us to make, because none of our family live in this country. How do you make this decision if you have an SN child?
Part of wanting the best for your children would be wanting them to have the freedom and ability to do whatever they want/are able to. This is for both TN and SN children, but what if you have both, a TN child has an SN sibling that needs major care? What then? How does a parent feel knowing that their TN child's future will be limited by caring for a SN sibling? I'm not saying they are not loving and caring people, I have no doubt that they are, but that's the point, isn't it? They love and care for their sibling, and that in itself places the limits.
I don't think I'm unusual in having these fears, and I doubt that many parents of SN children would willingly choose to have a child with SN, but once you have and love your child, then the SN is something you have to deal with. But it's also not unusual for people to NOT have children, because they are scared of the risk.
(But I do think it's kind of crass to say to a friend who has a SN child that you 'couldn't' cope in the way the OPs friend has.)