A child row does not appear in the view by using following code snippet:

GridViewRowInfo^ pNewRow = pTemplate->Rows->AddNew();
pNewRow->Cells["ChildNameColumn"]->Value = this->ChildTextBox->Text;
int count = radGridView1->ChildRows->Count;
pNewRow->Cells["ChildAddressColumn"]->Value = count.ToString()

Workaround: add new rows in the following manner:

private: System::Void button2_Click(System::Object^  sender, System::EventArgs^  e)
{
    // add child row
    GridViewTemplate^ pTemplate = radGridView1->MasterTemplate->Templates[0];
    GridViewRowInfo^ pNewRow = pTemplate->Rows->NewRow();
    pNewRow->Cells["ChildNameColumn"]->Value = this->ChildTextBox->Text;
    int count = radGridView1->ChildRows->Count;
    pNewRow->Cells["ChildAddressColumn"]->Value = count.ToString();
    pTemplate->Rows->Add(pNewRow);
}