Plenty of people are born into broken or dysfunctional families. As a species, humans have been through some tough times and survived through it. I don't think that should be a reason to not have children. I think it is better to learn through the mistakes of the past so they aren't repeated... and only then can each generation do better than their ancestors. I suspect it has been this way for thousands of years. It is motivation to do better by our own children than was done to us or those around, rather than being put off completely. But if you don't have that drive then it may be better to not have children.