To be fair, there are also millions of kids who have serious behavioral problems and are not adopted. Yes, there is a genetic and fetal component that may have an effect, but that’s why there’s the whole “nature vs nurture” debate. And the answer is that both are strong contributors. But even kids raised in a “normal” (i.e., financially comfortable, non-abusive, non-negligent) home with their biological parents can end up with behavioral problems, especially in puberty. There are millions of adopted kids with no such issues and millions of bio-kids with them, and vice versa. Short version: you never really know what you’re gonna get with a kid. All you can do is your best to raise them right. But there’s a difference between knowing there’s a real chance of behavioral issues and taking on a kid knowing that the behavioral issues are alive and well already. I have the utmost respect and admiration for the people who can do that, but there aren’t a ton of them, sadly. I don’t know anything about UK adoption law, but I would think parents could still choose to adopt out their baby even if they are capable, no? I don’t have statistics in front of me, but I believe the overwhelming majority of infant adoptions are completely voluntarily, considering courts will rarely terminate rights immediately and would give the biological parents a chance to get custody.