I agree, I really think that if guilty, the parents were the target of sadism, and the babies were the vessels to achieve that.
One of each of the first two pairs of twins survived, but not for want of (allegedly) trying to kill them too. Twins L and M survived but both had alleged attempts on their lives. Two of the triplets died and the parents begged for the surviving child to be transferred.
The triplets were naturally conceived and identical, something which only happens in every 200 million pregnancies. That significance would have been irresistible, if guilty.
I can't remember which babies are brain damaged, I know one is profoundly disabled but can't remember if it's a twin.
I think that was Baby G? Not a twin as far as I remember.