I combined them like so and it appears to be working correctly:
   [ParseChildren(true), PersistChildren(false)]
    public class Test : WebControl, INamingContainer
    {
        [ParseChildren(true, "Items")]
        public class iTestItems
        {
            private ListItemCollection _Items;
            [DefaultValue((string)null), MergableProperty(false), PersistenceMode(PersistenceMode.InnerDefaultProperty)]
            public virtual ListItemCollection Items
            {
                get
                {
                    if (_Items == null)
                        _Items = new ListItemCollection();
                    return _Items;
                }
            }
        }
        private iTestItems _TestItems = null;
        private ITemplate _ContentTemplate = null;
        public event EventHandler TestClick = null;
        [PersistenceMode(PersistenceMode.InnerProperty),
         TemplateContainer(typeof(iTestItems)),
         TemplateInstance(TemplateInstance.Single)]
        public iTestItems TestItems
        {
            get { return _TestItems; }
            set { _TestItems = value; }
        }
        [PersistenceMode(PersistenceMode.InnerProperty),
         TemplateContainer(typeof(TemplateControl)),
         TemplateInstance(TemplateInstance.Single)]
        public ITemplate ContentTemplate
        {
            get { return _ContentTemplate; }
            set { _ContentTemplate = value; }
        }
    }
Used:
<cc:Test ID="jqTestTest01" runat="server" OnTestClick="jqTestTest01_TestClick">
    <TestItems>
        <asp:ListItem Text="Tab One" Value="1" Selected="True" />
        <asp:ListItem Text="Tab Two" Value="2" />
        <asp:ListItem Text="Tab Three" Value="3" />
        <asp:ListItem Text="Tab Four" Value="4" />
        <asp:ListItem Text="Tab Five" Value="5" />
    </TestItems>
    <ContentTemplate>
        <asp:Label ID="lblTestTest01" runat="server" Text="None" />            
    </ContentTemplate>    
</cc:Test>