Photograph of the “Giant’s Hall” at the Hofburg Palace, showing some of the many portraits of the family of Maria Theresa.
The portraits that can be seen include (Click on them to see them bigger):
In the first portrait, I believe the boy is Carlo of Naples and Sicily and the girl is definitely Maria Theresa of Naples and Sicily. Both were children of Maria Christina of Austria, Maria Theresa’s daughter.
In the second portrait, we have Louis I of Etruria and one of his sisters, but I’m not certain which as the source identifies her as “Maria Josepha of Parma” and he had no sister by that name. Both were children of Maria Amalia of Austria, Maria Theresa’s daughter.
In the third portrait, we have Francis IV, Duke of Modena, and Maria Leopoldina of Austria-Este. Both were children of Archduke Ferdinand, Maria Theresa’s son.
In the the first portrait, we have Maria Josepha of Bavaria. She was the second wife of Joseph II, Maria Theresa’s son.
In the second portrait, we have representations of the three daughters of Maria Theresa who died in infancy. The eldest was named Maria Elisabeth, and the two younger ones were both called Maria Carolina.
In the third portrait, we have Isabella of Parma, the first wife of Joseph II, Maria Theresa’s son.