Imagine a medieval society composed entirely of women, with some small number of machines (let's say 7) which can take material from two women and combines it to create an embryo that's implanted in one of the women. The whole process is fast, let's say it takes one second from start to finish.
"Queens" have taken control of these machines, and any woman who wants to have children performs a pilgrimage to where a machine is located. The woman has an embryo implanted whose parents are her and the queen.
Clearly, all the children created through this process would be women, and half-sisters with many other people. What social norms (perhaps regarding family structure) could we expect to develop in this environment?
Edit: By "medieval" I mean medieval tech levels, so no electricity, no modern weaponry, poor sanitation, etc.