With the following code:
<ScrollView Orientation="Vertical" Padding="0">
<RelativeLayout BackgroundColor="Red" Padding="0">
<BoxView Color="Blue" WidthRequest="100" HeightRequest="100"
RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}"
RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}" />
</RelativeLayout>
<RelativeLayout BackgroundColor="Green" Padding="0">
<BoxView Color="Yellow" WidthRequest="100" HeightRequest="100"
RelativeLayout.XConstraint="{ConstraintExpression Type=Constant, Constant=0}"
RelativeLayout.YConstraint="{ConstraintExpression Type=Constant, Constant=0}" />
</RelativeLayout>
</ScrollView>
But for some reason, instead of stacking, each new relative layout takes up the whole screen like this:

Why won't they stack up vertically? Stack layouts would normally only take vertically or horizontally the combined height of their children, but this doesn't happen with relative layouts. What am I missing?