Wenceslaus I of Legnica
Wenceslaus I, Duke of Legnica( ca. 1318 – 2 June 1364) was a Duke of Namysłów from 1338 and of Legnica- Brieg from 1342 until his death, but with further divisions with his brother Louis I.
He was the eldest son of Bolesław III the Generous, Duke of Legnica- Brieg by his first wife, Margaret of Bohemia.
He was named after his maternal grandfather, King Wenceslaus II of Bohemia.
Frederick II of Legnica
Frederick II, Duke of Legnica( 12 February 1480 – 17 September 1547), also known as the Great of Legnica, was a Duke of Legnica from 1488( until 1495 and 1505 with his brothers), of Brzeg from 1521.
The most notorious of all Legnica Piast rulers, thanks to his excellent financial politics his Duchy was expanded to the Oder River, and he became the founder of the Duchy of Legnica- Wołów- Brzeg.
He was the second son of Frederick I, Duke of Chojnów- Oława- Legnica- Brzeg- Lubin, by his wife Ludmila, daughter of George of Poděbrady, King of Bohemia.
Wenceslaus II of Legnica
Wenceslaus II, Duke of Legnica( 1348 – 30 December 1419) was a Duke of Legnica from 1364( only nominal; from 1409 he reigned alone and personally) until 1413, Bishop of Lebus( 1375 – 82) and Breslau( Wroclaw)( 1382 – 1417; also Duke of Nysa-Otmuchów.
He was the second son of Wenceslaus I of Legnica, by his wife Anna, daughter of Casimir I, Duke of Cieszyn.
Hedwig of Legnica
Hedwig of Legnica( ca. 1351 – 1 August 1409) was a Polish princess and member of the Piast dynasty, in the Legnica branch.
By marriage Hedwig was Duchess of Żagań.
She was the fourth child and only daughter of Wenceslaus I, Duke of Legnica and his wife Anna, daughter of Casimir I, Duke of Cieszyn.
Sophia of Bavaria
Sophia of Bavaria (1376 – 4 November 1428) was a Queen of Bohemia and the spouse of Wenceslaus, King of Bohemia and King of the Romans.
She was briefly interim regent of Bohemia after the death of Wenceslaus in 1419.
Henry VIII of Legnica
Henry VIII of Legnica( ca. 1355 – 12 December 1398) was a Duke of Legnica since 1364( nominally and together with his brothers) and Bishop of Włocławek since 1389 until his death.
He was the fourth of Wenceslaus I, Duke of Legnica, by his wife Anna, daughter of Casimir I, Duke of Cieszyn.
Bolesław III the Generous
Boleslaw III the Wasteful( 23 September 1291 – Brieg, 21 April 1352), was a Duke of Legnica, Brzeg( Brieg) from 1296 until 1342, and Duke of Wrocław from 1296 until 1311.
He was the eldest son of Henry V the Fat, Duke of Legnica and Wrocław, by his wife Elisabeth, daughter of Bolesław the Pious, Duke of Greater Poland.
Rupert I of Legnica
Rupert I of Legnica( 27 March 1347 – by 12 January 1409) was a Duke of Legnica since 1364 until his death, and also regent over half of the Duchy of Głogów- Żagań during 1397 – 1401.
He was the eldest son of Wenceslaus I, Duke of Legnica, by his wife Anna, daughter of Casimir I, Duke of Cieszyn.
He was born after eight years of childless marriage.
Adam Wenceslaus, Duke of Cieszyn
Adam Wenceslaus of Cieszyn( 12 December 1574 – 13 July 1617), was a Duke of Cieszyn from 1579 until his death.
He was the second but only surviving son of Wenceslaus III Adam, Duke of Cieszyn, by his second wife Sidonia Katharina, daughter of Francis I, Duke of Saxe- Lauenburg.
His older half- brother, Frederick Casimir, only son of Wenceslaus III Adam's first marriage, died a few years before he was born, in 1571.
Bolesław IV of Legnica
Bolesław IV of Legnica( ca. 1349 – 3/4 March 1394) was a Duke of Legnica since 1364( nominally; together with his brothers).
He was the third son of Wenceslaus I, Duke of Legnica by his wife Anna, daughter of Casimir I, Duke of Cieszyn.

Question: When is Wenceslaus I Of Legnica's father's birthday?
Answer: 23 September 1291