Prince Sixtus of Bourbon-Parma
Prince Sixtus of Bourbon-Parma (1 August 1886 – 14 March 1934) was a member of the House of Bourbon-Parma, a Belgian officer in World War I, and the central figure in the Sixtus Affair, an attempt to negotiate a treaty to end Austria-Hungary's participation in the Great War separate from its Central Powers allies.
He also wrote a number of books.
Prince Charles of Luxembourg
Prince Charles of Luxembourg, Prince of Bourbon- Parma and Nassau( Charles Frédéric Louis Guillaume Marie; 7 August 1927 – 26 July 1977), was a younger son of Grand Duchess Charlotte and Prince Felix of Bourbon- Parma.
Princess Carolina, Marchioness of Sala
Princess Maria" Carolina" Christina of Bourbon- Parma, Marchioness of Sala( born 23 June 1974), is the fourth and youngest child of Princess Irene of the Netherlands and Carlos Hugo, Duke of Parma, and is a member of the Royal and Ducal House of Bourbon- Parma, as well as of the Dutch Royal Family.
Princess Marie-Françoise of Bourbon-Parma
Princess Marie- Françoise Antoinette Jeanne Madeleine of Bourbon- Parma( born 19 August 1928) is a French- Italian humanitarian and the founder of the Malte Liban Association in Lebanon.
She is a princess of the House of Bourbon- Parma by birth and a princess of the House of Lobkowicz through marriage.
Infanta Maria Antonia of Portugal
Infanta Maria Antónia of Portugal
(Portuguese: "Maria Antónia
Adelaide Camila Carolina Eulália
Leopoldina Sofia Inês Francisca de Assis e de Paula Micaela Rafaela Gabriela Gonzaga Gregória Bernardina Benedita Andrea"
; 28 November 1862 – 14 May 1959) was a Portuguese infanta, the seventh and last child of Miguel of Portugal and
Adelaide of Löwenstein-Wertheim-Rosenberg.
Prince René of Bourbon-Parma
Prince René of Bourbon-Parma (17 October 1894 – 30 July 1962) was the seventh surviving son of Robert I, Duke of Parma, and his second wife, Infanta Maria Antonia of Portugal.
In 1921, he married Princess Margaret of Denmark.
They had four children including Queen Anne of Romania, the wife of Michael I, former King of Romania.
Princess Margaret of Denmark
Princess Margaret of Denmark
( Margrethe Françoise Louise Marie Helene; 17 September 1895 – 18 September 1992) was a Danish princess by birth and a princess of Bourbon- Parma as the wife of Prince René of Bourbon- Parma.
She was the youngest grandchild of Christian IX of Denmark and Queen Louise.
Prince Michel of Bourbon-Parma
Prince Michel of Bourbon- Parma
( Michel Marie Xavier Waldemar Georg Robert Karl Eymar; 4 March 1926 – 7 July 2018) was a French businessman, soldier and racing car driver, who was a member of deposed sovereign ducal House of Bourbon- Parma.
He was a son of Prince René of Bourbon- Parma and his wife Princess Margaret of Denmark.
Paternally, he was a grandson of Robert I, Duke of Parma( 1848 – 1907), while through his mother he was a great- grandson of Christian IX of Denmark.
Prince Michel was also the younger brother of Queen Anne of Romania.
Archduchess Maria Anna of Austria (1882–1940)
Archduchess" Maria Anna" Isabelle Epiphanie Eugenie Gabriele of Austria, full German name:" Maria Anna Isabelle Epiphanie Eugenie Gabriele, Erzherzogin von Österreich"( 6 January 1882, Linz, Upper Austria, Austria – Hungary – 25 February 1940, Lausanne, Vaud, Switzerland) was a member of the Teschen branch of the House of Habsburg- Lorraine and an Archduchess of Austria and Princess of Bohemia, Hungary, and Tuscany by birth.
Through her marriage to Prince Elias of Bourbon- Parma( later Duke of Parma), Maria Anna was also a member of the House of Bourbon- Parma and a Princess of Bourbon- Parma.
Princess Margarita, Countess of Colorno
Princess Margarita Maria Beatriz of Bourbon-Parma, Countess of Colorno (born 13 October 1972), is the eldest daughter of Princess Irene of the Netherlands and Carlos Hugo, Duke of Parma, and is member of the Royal and Ducal House of Bourbon-Parma, as well of the Dutch Royal Family.

Question: Who is the maternal grandmother of Prince René Of Bourbon-Parma?
Answer: Adelaide of Löwenstein-Wertheim-Rosenberg