Xamarin Forms ListView with HasUnEvenRows=True Occupies complete screen - xamarin.forms

Question

I have different views along with ListView on my screen. ListView almost fills the screen and elements below the ListView are not visible. I have set HasUnEvenRows=True because each list item has different height.
<StackLayout Spacing="0">
<local:PageHeader></local:PageHeader>
<Grid Padding="25,15,25,10" Grid.RowSpacing="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="Auto"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
<RowDefinition Height="Auto"></RowDefinition>
</Grid.RowDefinitions>
<Label Grid.Column="0" Grid.Row="0" VerticalOptions="CenterAndExpand" Grid.ColumnSpan="1" Text="{local:Translate FROM_COLON}" FontSize="18"></Label>
<StackLayout Orientation="Vertical" Grid.Column="1" Grid.Row="0" Grid.RowSpan="3" Grid.ColumnSpan="3">
<Label Text="{Binding Group}" TextColor="{x:Static local:ColorUtils.DarkBlue}" FontStyle="Bold" FontSize="18"></Label>
<Label Text="{Binding Sender, StringFormat='<{0}>'}" TextColor="{x:Static local:ColorUtils.DarkBlue}" FontSize="18"></Label>
</StackLayout>
<ContentView Grid.Column="0" Grid.Row="1" Grid.ColumnSpan="3" Padding="0,15,0,0">
<Button Text="{Binding DetailsButtonTitle}" Clicked="OnDetailButtonClick" BackgroundColor="Transparent" TextColor="{x:Static local:ColorUtils.DarkBlue}" HorizontalOptions="Start" VerticalOptions="StartAndExpand" Padding="0"></Button>
</ContentView>
<Button Grid.Column="3" Grid.Row="1" Grid.RowSpan="{Binding ReplyButtonRowSpan}" Text="{local:Translate REPLY}" Image="reply_arrow_small" BackgroundColor="Transparent" TextColor="{x:Static local:ColorUtils.Gray}" HorizontalOptions="End" VerticalOptions="EndAndExpand" Padding="0" FontSize="13" WidthRequest="65" Clicked="OnReplyButtonClick"></Button>
<Label Grid.Column="0" Grid.Row="2" Grid.ColumnSpan="3" IsVisible="{Binding IsDetailShown, Converter={local:NotConverter Convert}}" Text="{Binding HumanizedDateFormat}" TextColor="{x:Static local:ColorUtils.Gray}"></Label>
<ContentView Padding="0,0,0,5" Grid.Column="0" Grid.Row="2" IsVisible="{Binding IsDetailShown}" >
<Label Text="{local:Translate FROM_COLON}" TextColor="{x:Static local:ColorUtils.Gray}" FontStyle="Bold" />
</ContentView>
<StackLayout Orientation="Horizontal" Grid.Column="1" Grid.Row="2" Grid.RowSpan="2" Grid.ColumnSpan="3" IsVisible="{Binding IsDetailShown}">
<Label VerticalTextAlignment="Start" Text="{Binding Group}" TextColor="{x:Static local:ColorUtils.Gray}" FontStyle="Bold" />
<Label VerticalTextAlignment="Start" Text="{Binding Sender, StringFormat='<{0}>'}" TextColor="{x:Static local:ColorUtils.Gray}"></Label>
</StackLayout>
<Label Grid.Column="0" Grid.Row="4" Grid.RowSpan="1" IsVisible="{Binding IsDetailShown}" Text="{local:Translate TO_COLON}" TextColor="{x:Static local:ColorUtils.Gray}" FontStyle="Bold" />
<ListView x:Name="ListToAddresses" Grid.RowSpan="1" Grid.Column="1" Grid.Row="4" Grid.ColumnSpan="3" IsVisible="{Binding IsDetailShown}" HeightRequest="{Binding ListHeight}" VerticalOptions="Start" HasUnevenRows="True" CachingStrategy="RecycleElement" ItemsSource="{Binding Recipients}" SeparatorVisibility="None">
<ListView.ItemTemplate>
<DataTemplate>
<ViewCell IsEnabled="False">
<StackLayout VerticalOptions="Start" Padding="0,0,0,12" >
<Label Text="{Binding Path=Key}" VerticalTextAlignment="Start" TextColor="{x:Static local:ColorUtils.Gray}" FontStyle="Bold" VerticalOptions="Start" />
<Label Text="{Binding Path=Value}" VerticalTextAlignment="Start" TextColor="{x:Static local:ColorUtils.Gray}" VerticalOptions="Start" />
</StackLayout>
</ViewCell>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
<ContentView Padding="0,5,0,0" Grid.Column="0" Grid.Row="5" IsVisible="{Binding IsDetailShown}">
<Label Text="{local:Translate DATE_COLON}" TextColor="{x:Static local:ColorUtils.Gray}" FontStyle="Bold" />
</ContentView>
<Label Grid.Column="1" Grid.Row="5" Grid.ColumnSpan="3" VerticalTextAlignment="End" IsVisible="{Binding IsDetailShown}" Text="{Binding LongDateFormat}" TextColor="{x:Static local:ColorUtils.Gray}"></Label>
</Grid>
<BoxView HeightRequest="1" BackgroundColor="{x:Static local:ColorUtils.LightGray}"></BoxView>
<ContentView Padding="25,15,25,0">
<Label Text="{Binding Description}" FontSize="18"></Label>
</ContentView>
</StackLayout>