Siemowit I of Masovia
Siemowit I of Masovia( c. 1224/28 – 23 June 1262), was a Polish prince member of the House of Piast, Duke of Czersk during 1247- 1248, Duke of Masovia( except Dobrzy ń) during 1248- 1262, ruler over Sieradz during 1259- 1260.
He was the sixth son of Konrad I of Masovia and his wife Agafia of Rus.
He was named after his older brother Siemowit, who died young in 1224.
Anna of Masovia
Anna of Masovia( c. 1498 – after 26 January 1557 in Jaroslaw) was Princess of Mazovia and a member of the House of Piast.
She was the last representative of the line of Masovian- Piast.
She was the second daughter of Konrad III of Masovia and Anna Radziwiłł.
She was a sister of Dukes Janusz III of Masovia and Stanislaus of Masovia, and Sophia, who married Stephen VII Báthory.
Sophia of Masovia
Sophia of Masovia (1497/1498 - before 11 March 1543) was a Princess of Masovia, daughter of Konrad III Rudy, Duke of Masovia and his wife Anna Radziwiłł.
She was a member of the House of Piast.
On 17 September 1520 in Warsaw, Sophia was married by proxy to Stephen VII Báthory.
On 17 January 1521, Sophia and her entourage went to Hungary, where in February there was a formal marriage.
The couple had three children: Anna, Stephen and Klara; however, other sources claim that Klara was the couple's only child.
Klara was engaged to Carl, Duke of Münsterberg, but died in 1535, before the marriage took place.
After the death of Stephen in 1530, Sophia was married to Croatian magnate Louis Pekry.
Sophia's second marriage was childless.
She then died sometime before 11 March 1543.
Sophia had three siblings:
Stanislaus I of Masovia, Janusz III of Masovia and Anna of Masovia, both her brothers died childless and so Anna and Sophia were the last Masovian Piasts.
Soon after Janusz's death, the Duchy of Masovia was annexed into the kingdom of Poland, despite resistance from some of the Masovian nobility.
They tried to retain their independence and argued that the Duchy should be inherited by the female relatives (such as Anna or Sophia).
The Polish king refused to recognize their demands.
Anna was made titular Duchess of Masovia.
Anna Radziwiłł (nobility)
Anna Radziwiłłówna  (1475 or 1476 – 15 March 1522) was a Lithuanian noble woman and Duchess of Masovia.
She was the daughter of Mikołaj Radziwiłł and his first wife, Zofia Moniwidówna.
She was born in 1475 or 1476.
Anna was married to Konrad III Rudy of the Masovian Piast Dynasty between 29 September 1496 and 2 April 1497.
She died on the night of 14/15 March 1522.
She was buried in the cloister of Bernardin's in Warsaw.
She is one of the characters on the famous painting by Jan Matejko, "Prussian Homage".
Margaret of Masovia
Margaret of Masovia( before 1358 – 14 May 1388/4 April 1396) was Duchess of Pomerania and Brzeg, by her marriages to Casimir IV, Duke of Pomerania and then to Henryk VIII with a Scar.
She was a member of the House of Piast.
Margaret was a daughter of Siemowit III of Masovia and his wife Euphemia of Opawa.
Her paternal grandparents were Trojden I of Masovia and his wife Maria, daughter of Yuri I of Galicia and Euphemia of Kuyavia.
Theodred II (Bishop of Elmham)
Theodred II was a medieval Bishop of Elmham.
The date of Theodred's consecration unknown, but the date of his death was sometime between 995 and 997.
Etan Boritzer
Etan Boritzer( born 1950) is an American writer of children ’s literature who is best known for his book" What is God?" first published in 1989.
His best selling" What is?" illustrated children's book series on character education and difficult subjects for children is a popular teaching guide for parents, teachers and child- life professionals.
Boritzer gained national critical acclaim after" What is God?" was published in 1989 although the book has caused controversy from religious fundamentalists for its universalist views.
The other current books in the" What is?" series include
What is Love?,
What is Death?,
What is Beautiful?,
What is Funny?,
What is Right?,
What is Peace?,
What is Money?,
What is Dreaming?,
What is a Friend?,
What is True?,
What is a Family?,
What is a Feeling?"
The series is now also translated into 15 languages.
Boritzer was first published in 1963 at the age of 13 when he wrote an essay in his English class at Wade Junior High School in the Bronx, New York on the assassination of John F. Kennedy.
His essay was included in a special anthology by New York City public school children compiled and published by the New York City Department of Education.
Boritzer now lives in Venice, California and maintains his publishing office there also.
He has helped numerous other authors to get published through" How to Get Your Book Published!" programs.
Boritzer is also a yoga teacher who teaches regular classes locally and guest- teaches nationally.
He is also recognized nationally as an erudite speaker on" The Teachings of the Buddha."
Gaudemunda of Lithuania
Gaudemunda Sophia of Lithuania( also Gaudimantė; c. 1260 – 1288/1313) was the daughter of Traidenis, Grand Duke of Lithuania( c. 1270 – 1282).
In 1279 she married Duke of Masovia Bolesław II( c. 1254–1313) of the Piast dynasty.
He was the son of Ziemowit I, Prince of Masovia, and Pereyaslava, daughter of Daniel of Galicia of the Rurik dynasty.
Her husband united the Duchy of Masovia and then divided it between their sons, who were:
Siemowit III, Duke of Masovia
Siemowit III of Masovia( his name also rendered Ziemowit; – 1381) was a prince of Masovia and a co-regent( with his brother Casimir I of Warsaw) of the lands of Warsaw, Czersk, Rawa, Gostynin and other parts of Masovia.
Agnieszka (courtier)
Agnieszka( died after 1572), was a Polish Court dwarf in service of Sophia Jagiellon, Duchess of Brunswick- Lüneburg.
She was the personal favorite and secretary of Sophia.
Agnieszka was likely in the service of Sophia in Poland prior to her marriage.
She did belong to the Polish retinue of 500 people accompanying Sophia from Poland to her new life in Germany upon her marriage to Henry V, Duke of Brunswick- Lüneburg in February 1556.
In contrast to the majority of the Polish courtiers, Agnieszka remained with Sophia in her new court in Germany in Wolfenbüttel Castle.
She had an influential position at court as the personal confidante and secretary of Sophia.
She conducted the correspondence between Sophia and her powerful relatives, such as her brother the king of Poland and her sister the queen of Sweden.
In 1568, she accompanied Sophia to her dower court, and assisted her in making it a cultural center.
After 1572, she assisted Sophia in her work to defend her late brother's will.
Her year of death is not known, but she was noted to be alive in 1572.
Her position is mirrored with Dorothea Ostrelska, whose life in the court of Sophia's sister Catherine Jagellon is an almost exact replica to her.

Question: What is the date of birth of Sophia Of Masovia's mother?