Henry II, Margrave of Brandenburg-Stendal
Henry II of Brandenburg- Stendal, nicknamed
Henry the Younger or Henry the Child( – July 1320) was the last Margrave of Brandenburg from the House of Ascania.
Agnes of Bavaria, Margravine of Brandenburg-Stendal
Agnes of Bavaria (1276–1345) was a daughter of Duke Louis II of Upper Bavaria (1229–1294) and his third wife, Matilda of Habsburg (1253–1304).
In 1290, in Donauwörth, she married Henry "the Younger" of Hesse (1265 – 23 August 1298), a son of Landgrave Henry I of Hesse (1244–1308).
They had at least one child:
In 1303, she remarried to Margrave Henry I of Brandenburg-Stendal (1256–1318).
From her second marriage, she had three children:
Adela of Louvain (d.1083)
Adela of Louvain( d.1083) was margravine of Meissen and later, margravine of the Saxon Ostmark.
Margaret of Baden
Margaret of Baden( 1431 – 24 October 1457) was a Margravine of Baden by birth and by marriage Margravine of Brandenburg- Ansbach and Brandenburg- Kulmbach.
She was the daughter of Jacob, Margrave of Baden- Baden, and his wife Catherine of Lorraine.
In 1446, Margaret married Albert of Brandenburg, the future Albert III Achilles, Elector of Brandenburg, in Heilsbronn.
Margaret died before he succeeded to the Electorate of Brandenburg, thus never served as Electress.
Their marriage produced three sons and three daughters:
Margaret died in Ansbach in 1457 shortly after her husband acquired the Margraviate of Brandenburg- Kulmbach.
Minamoto no Chikako
She was the mother of Prince Morinaga.
Herman, Margrave of Brandenburg-Salzwedel
Herman, Margrave of Brandenburg, also known as" Herman the Tall"( – 1 February 1308), a member of the House of Ascania, was Margrave and co-ruler of Brandenburg with his cousin Margrave Otto IV of Brandenburg- Stendal.
Catherine of Brandenburg-Küstrin
Catherine of Brandenburg- Küstrin( 10 August 1549 – 30 September 1602) was a Margravine of Brandenburg- Küstrin by birth and Electress of Brandenburg by marriage.
Elisabeth of Brandenburg-Küstrin
Elizabeth of Brandenburg- Küstrin( 29 August 1540 – 8 March 1578), was a princess of Brandenburg- Küstrin and margravine of Brandenburg- Ansbach and Brandenburg- Kulmbach by marriage.
Matilda of Habsburg
Matilda of Habsburg or Melchilde (1253 in Rheinfelden – 23 December 1304 in Munich, Bavaria) was the eldest daughter of Rudolph I of Germany and Gertrude of Hohenburg.
She was regent of Bavaria in the minority of her son.
Agnes of Waiblingen
Agnes of Waiblingen( 1072/ 73 – 24 September 1143), also known as Agnes of Germany, Agnes of Poitou and Agnes of Saarbrücken, was a member of the Salian imperial family.
Through her first marriage, she was Duchess of Swabia; through her second marriage, she was Margravine of Austria.

Question: Where was the mother of Agnes Of Bavaria, Margravine Of Brandenburg-Stendal born?
Answer: Rheinfelden