It doesn't really take much working out Holly so I will let you ponder the issue.
Unfortunate? When you have children you really don't know how they will turn out, similarly, when you adopt, there are NO guarantees. One can only do ones best and that is what Nevile and June attempted. They taught them right from wrong but both of them rebelled in different ways...bad luck all round imo.

June Bamber with adopted children Sheila and Jeremy with family pet Crispy in happier times.
(Jeremy was later to kill them all claiming they had worthless lives)
John, I agree entirely that there are no guarantees about how children will turn out, BUT biological children, for the MOST part will have much about them which has been handed down from his/her parents. Adopted children don't have those genetics to fall back on so it's possible they could find themselves living with one or both parents whose concepts are innately alien to them.
Whilst it can't be said to be true of ALL adoptive parents, like biological parents we have to look at their own childhood experiences to understand what sort of parents they're likely to become. I think it highly likely that June had the same expectations of HER children as her mother had of her, ie duty, obedience and responsibility to parents, society and God. Whilst her biological children would have probably been genetically predisposed to the concept, her adopted children may have -and I think probably DID- see it as harsh and restrictive. For all that, June was a good, devoted woman -I've never heard a bad word said about her- who, I believe, within her own parameters, limited, but she had no other frame of reference, did the best she knew how. Sadly, I believe that because neither Jeremy nor Sheila conformed to her expectations, it's likely that June became overwhelmed and felt that others would judge her to have failed.