Alignparentbottom for relativelayout inside scrollview

I'm trying to put some content (in this case LL with id "bottomcontent") at the bottom of the screen, and when the user starts scrolling, I like to show more content at the bottom of the screen. Any ideas how to do this? I have the following code, but no scrolling as LL below "bottomcontent" gets height = 0

Here is the code:
<ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MyActivity"
        android:background="@android:color/transparent"
        android:fillViewport="true"
        android:layout_alignParentTop="true">
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical">
            <!-- I expect this to occupy one full screen, since its child is asking for align parent bottom = true-->
            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@android:color/transparent"
                android:id="@+id/top">
                <LinearLayout
                    android:id="@+id/bottomcontent"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:background="@android:color/holo_green_dark"
                    android:layout_alignParentBottom="true"
                    >

                    <TextView
                        android:text="@string/hello_world"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:background="@android:color/holo_red_light"
                        />
                </LinearLayout>
            </RelativeLayout>
            <!-- When user scrolls, I expect this linear layout to be seen. But I get its height to be zero, so no scrolling-->
            <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"
                >


                <TextView
                    android:text="hello_world hello_world hello_world hello_world hello_world hello_world hello_world "
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:background="@android:color/holo_blue_dark"
                    />
            </LinearLayout>

        </LinearLayout>
    </ScrollView>