MainView.xaml

<UserControl x:Class="Example.View.MainView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:ViewModel="clr-namespace:Example.ViewModel"
    xmlns:View="clr-namespace:Example.View"
    xmlns:dxmvvm="http://schemas.devexpress.com/winfx/2008/xaml/mvvm"
    xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" d:DesignHeight="500" d:DesignWidth="600"
    DataContext="{dxmvvm:ViewModelSource ViewModel:MainViewModel}">

    <dxmvvm:Interaction.Behaviors>
        <dx:DXMessageBoxService/>
    </dxmvvm:Interaction.Behaviors>

    <Grid x:Name="LayoutRoot" Background="White">
        <StackPanel Orientation="Vertical">
            <StackPanel Orientation="Horizontal">
                <Button Content="Change Parameter1" Command="{Binding ChangeParameter1Command}"/>
                <Button Content="Change Parameter2" Command="{Binding ChangeParameter2Command}"/>
            </StackPanel>
            <StackPanel Orientation="Horizontal">
                <Border BorderThickness="1" BorderBrush="Black" Margin="10" Width="300" Height="100">
                    <View:ChildView1 dxmvvm:ViewModelExtensions.ParentViewModel="{Binding DataContext, ElementName=LayoutRoot}"
                                     dxmvvm:ViewModelExtensions.Parameter="{Binding DataContext.Parameter1, ElementName=LayoutRoot}"/>
                </Border>
            </StackPanel>
            <StackPanel Orientation="Horizontal">
                <Border BorderThickness="1" BorderBrush="Black" Margin="10" Width="300" Height="100">
                    <View:ChildView2 dxmvvm:ViewModelExtensions.ParentViewModel="{Binding DataContext, ElementName=LayoutRoot}"
                                     dxmvvm:ViewModelExtensions.Parameter="{Binding DataContext.Parameter2, ElementName=LayoutRoot}"/>
                </Border>
            </StackPanel>
        </StackPanel>
    </Grid>
</UserControl>