MVC Razor create list of objects to submit

I am an experienced .NET C# Software Developer, however only a few months ago i started worked with MVC Razor (MVC 5).

I have a small situation that i couldn't find any answer to on the net(after hours of searching)

I have a Model that has a list of another Model which in turn also has a list of a model as shown below.

public class Parent
{
    public string Name { get; set; }
    public string Sex { get; set; }
    public int Age { get; set; }
    public List<Child> Children { get; set; } 
}

public class Child
{
    public string Name { get; set; }
    public string Sex { get; set; }
    public int Age { get; set; }
    public List<GrandChild> GrandChildren { get; set; } 
}

public class GrandChild
{
    public string Name { get; set; }
    public string Sex { get; set; }
    public int Age { get; set; }
}

and my Controller has 2 methods, one is main Get, and the other one is post in order to post new data

public ActionResult Index()
{
    return View();
}

[HttpPost]
public ActionResult PostParent(Parent parent)
{
    if (ModelState.IsValid)
    {
        //Do an insert to the DB
        return View("~/Views/Home/Index.cshtml");
    }

    return Json("Error");
}

However in my View in Form, i cannot find a way to create an add button and insert new data to the list of Children and GrandChildren(incase of a Child)

@using (Html.BeginForm("PostParent", "Home", FormMethod.Post, new {@class = "form-horizontal", role = "form"}))
{
    @Html.LabelFor(x => x.Name)
    @Html.TextBoxFor(x => x.Name)
}

I can only add fields for primitive type properites, but not for Objects.

I would really appreciate any Help!