In french, that relationship was called "freres de lait" (milk brothers,
or brothers in milk)

Louise, it would be interesting to trace this back and see if it was an
Islamic influence on French culture, via the Crusades or the Moors in
Spain... For in Islam this is true. Milkbanks in Singapore used to have two
kinds of milk, clearly separated in different freezers: that from mothers
of boys, to be given to boys, and that from mothers of girls, to girls.
This was because it would be incest for the milk brother to marry a milk
sister. Single sex unions were not culturally acceptable!

Naomi, in reply to your request for info on attitudes to breastmilk etc. I
reviewed all this and a lot more in a very substantial, heavily referenced
paper commissioned by Wellstart EPB, on Human Milk Expression and Storage
in Developing Countries. Although the published version is very much
edited, it should still be available from Wellstart in some form. I will
get around to publishing the full version one of these days, when there's
time..When you spend time really looking there is lots in anthropological,
historical and other resources, much of it plagiarised from earlier work I
might add. Wellstart in San Diego will have a copy of both the shorter
(lost most references too) and the longer versions. I don't have their
e-mail, alas.

Maureen