View to display a master and the first child?

I have two node types - A and B. B has a nodereference to A, thus one A (parent) has many B children:
A1
|-B11
|-B12
|-B13
...

A2
|-B21
|-B22
|-B23
...

I need a view that displays a row per A-node along with one of A's children (the first, a random, etc.). Example:

A1 B11

A2 B21

A3 B31

I saw a podcast showing how to do the reverse: for each child, use the Views relationships to show the parent's title for example. That's clear but I need it top-down: for each parent show one child. How can I do this with views?