Enno Louis, Prince of East Frisia
Enno Louis of East Frisia, was count of East Frisia and after 1654 "Fürst (Prince) of East Frisia", (29 October 1632 – Aurich, 4 April 1660) and the son of Ulrich II and Juliana of Hesse-Darmstadt.
Catherine Vasa of Sweden
Catherine Vasa of Sweden (6 June 1539 – 21 December 1610) was a Swedish princess, and the Countess consort of East Frisia as the spouse of Edzard II, Count of East Frisia.
She was the oldest daughter of Gustav Vasa and Margareta Leijonhufvud.
She was the autonomous Regent of and Norden in Ostfriesland (East Frisia) from 1599 to 1610.
Johan I of East Frisia
Johan I of East Frisia( 1506 – 1572) was a member of the house of Cirksena and a non-reigning Count of East Frisia and later imperial governor of Limburg.
His father, Edzard the Great, had introduced primogeniture in the county of East Frisia, so that his older brother Enno II of East Frisia inherited the county alone and he had to hold back.
Despite his ambitions, he always acknowledged his brother's rights and did not dispute the inheritance.
Unlike his father and his brother, Johan remained a Catholic.
After his father's death, he joined the imperial army.
However, he soon returned to East Frisia and began supporting his brother.
He had, however, little positive impact on his brother, who ruled unwisely.
Johan was unable to distinguish himself, and also took some unwise and ill- advised actions, such as those that lead to the Guelders feud.
He may also have encouraged Enno to try to re-introduce Catholicism in East Frisia.
This attempt was cut short when Enno died in 1540.
Enno's widow, Anna became regent for her son Edzard II.
Johan had an endless series of conflicts with Anna.
In 1538, Johan married Dorothea of Austria, the illegitimate daughter of Emperor Maximilian I. In 1543, Emperor Charles V reminded Johan of the fact that he was still, technically, in the imperial service.
Charles appointed Johan as stadtholder of the Duchy of Limburg, Falkenburg and Dalheim.
From that time onwards, Johan was colloquially called" Count Johan of Falkenburg".
His descendants lived at Coldeborg Castle in the Rheiderland and were financially supported by the counts of East Frisia.
Christine Charlotte of Württemberg
Christine Charlotte of Württemberg( 21 October 1645, Stuttgart – 16 May 1699, Bruchhausen) was a princess consort of East Frisia by marriage to George Christian, Prince of East Frisia.
She served as the regent of East Frisia during the minority of her son from 1665 until 1690.
Ulrich II, Count of East Frisia
Ulrich II of East Frisia, was count of East Frisia, (6 July 1605 – Aurich, 1 November 1648) was the fifth child and the third son of Enno III, Count of East Frisia and Anna of Holstein-Gottorp.
He inherited the East Frisia after the unexpected death of his brother Rudolf Christian on 17 April 1628.
He reigned during the Thirty Years' War.
East Frisia did not participate in the war, but general Ernst von Mansfeld quartered his troops in East Frisia, causing great distress.
The only exception was Emden because of the recently completed city wall, the city of Emden was protected against foreign troops.
Edzard II, Count of East Frisia
Edzard II, Count of East Frisia was count of East Frisia,( 24 June 1532, in Greetsiel – 1 March 1599, in Aurich) and the son of En no II of East Frisia and Anna of Oldenburg.
During his reign, he came into conflict with the city of Emden.
Edzard was a staunch Lutheran while the city of Emden was mostly Calvinistic.
In 1595 Emden revolted and, after an intercession by the Calvinistic Dutch Republic, Edzard was forced to accept a large degree of independence from Emden.
Ulrich I, Count of East Frisia
Ulrich I of East Frisia, first count of East Frisia,( Norden, 1408 – Emden, 25 or 26 September 1466) was a son of the chieftain Enno Edzardisna of Norden and Greetsiel, and Gela of Manslagt.
Enno I, Count of East Frisia
Enno I of East Frisia, count of East Frisia( 1 June 1460 – Friedeburg, 19 February 1491) was the eldest son of Ulrich I of East Frisia and Theda Ukena, of a chiefly East Frisian family.
Anna of Holstein-Gottorp
Anna of Holstein-Gottorp (27 February 1575 – 24 April 1610) was a German noblewoman, daughter of Duke Adolf of Holstein-Gottorp and Landgravine Christine of Hesse (daughter of Landgrave Philip I of Hesse).
On 28 January 1598, she married Count Enno III of East Frisia.
They had the following children:
Rudolf Christian, Count of East Frisia
Rudolf Christian of Ostfriesland, Count of East Frisia, was count of East Frisia, (Hage, 2 June 1602 – Hage, 17 April 1628) and the second son of Enno III, Count of East Frisia and Anna of Holstein-Gottorp.
During his reign, foreign troops participating in the Thirty Years' War began retreating into and quartering in East Frisia.
Also during his reign, fen exploitation in East Frisia begins.
He reached a settlement with the East Frisian Estates, who them paid him homage, ultimately even the city of Emden did so.
Under his leadership, the Harlingerland was finally incorporated in the county of East Frisia.
This is visible in the county's coat of arms, which was introduced under his rule in 1625 and remained in use until the county was annexed by Prussia in 1744.
At the age of just 26, he got embroiled in a fight with a lieutenant of the army of general Matthias Gallas, which was quartered in Berum Castle.
He was stabbed in the left eye, and died of his wound.
Since Rudolf Christian was childless, he was succeeded as Count of East Frisia by his brother Ulrich II.

Question: Who is Ulrich Ii, Count Of East Frisia's maternal grandmother?
Answer: Christine of Hesse