A bit of info:
The "
Diakonie is the social welfare organisation of Germany's Protestant churches. Our mission is to practice charity in the model of Jesus Christ."
The Matthäuskirche in Bergtheim (Ivar B.) is Evangelical Lutheran which is also Protestant faith.
CB's adoption could well have been arranged by the protestant church.
The Evangelical Lutherian church stood for many adoptions in Germany with over 60 adoption agencies under their wing. *1992
Adoptions in West Germany: Attitudes of Social Workers on JSTOR
It would be interesting to know if Mr/Mrs B were religious people and if the adoption was done through the church, maybe it was even a requirement that 'adopters' had to be active members of the church to be able to adopt?
It seems that Mrs B might have returned CB to the same 'institution' she originally got him from when he was a baby.
My initial thoughts on Ivar B were actually that he could in some way be related to MrB, a brother or uncle maybe, which somehow led me to this. It could be just a coincidence that Ivar B the priest shares the surname of course.
@BIZCOCHO