Equal height rows in a flex container

Question

As you can see, the list-items in the first row have same height. But items in the second row have different height

Answer 1

This seems to be working in cases with fixed parent height (tested in Chrome and Firefox):

.child {
        height    : 100%;
        overflow  : hidden;
}

.parent {
        display: flex;
        flex-direction: column;
        height: 70vh; // ! won't work unless parent container height is set
        position: relative;
}

If it's not possible to use grids for some reason, maybe it's the solution.