Melchior of Brunswick-Grubenhagen
Melchior of Brunswick- Grubenhagen( died 1381 or 1384) was a German aristocrat, prince- bishop of Osnabrück from 1369, and then prince- bishop of Schwerin from 1376 to 1381.
He was the son of Henry II, Duke of Brunswick- Grubenhagen.
Ernest I, Duke of Brunswick-Grubenhagen
Ernest I of Brunswick- Grubenhagen( – 9 March 1361) was Prince of Brunswick- Grubenhagen.
Anna of Brunswick-Grubenhagen-Einbeck
Anna of Brunswick- Grubenhagen- Einbeck( 1414 – 4 April 1474) was a daughter of Duke Eric I of Brunswick- Grubenhagen and his wife, Elisabeth of Brunswick- Göttingen.
Anna's first marriage was with Duke Albert III of Bavaria.
They had the following children:
After Albert's death, she married Duke Frederick III of Brunswick- Calenberg- Göttingen.
This marriage remained childless.
Henry IV, Duke of Brunswick-Grubenhagen
Duke Henry IV of Brunswick Grubenhagen( 1460 – 6 December 1526, Salzderhelden, now part of Einbeck) was a member of the Guelph dynasty and was Prince of Brunswick- Grubenhagen.
Ernest III, Duke of Brunswick-Grubenhagen
Ernest III of Brunswick- Grubenhagen- Herzberg( by a different counting: Ernest IV; 17 December 1518 in Osterode am Harz – 2 April 1567 in Herzberg Castle, Herzberg am Harz), was a member of the noble family of Guelph and a duke of Brunswick- Grubenhagen.
Eric I, Duke of Brunswick-Grubenhagen
Eric I, Duke of Brunswick- Grubenhagen nicknamed" the winner"( – 28 May 1427), ruled the Principality of Grubenhagen, a part of the Duchy of Brunswick- Lüneburg.
William, Duke of Brunswick-Grubenhagen
William of Brunswick- Grubenhagen( – 1360) was a Prince of Brunswick- Grubenhagen.
Helvis of Brunswick-Grubenhagen
Helvis of Brunswick-Grubenhagen (1353 – 15 January 1421), was the Queen consort of Cyprus and Queen consort of Armenia as the wife of King James I of Cyprus.
He was also titular King of Jerusalem.
She was styled Queen of Cyprus from 1382 to 1398; although at the time of his ascension to the Cypriot throne, he and Helvis were imprisoned in Genoa after they had been captured by the Genoese on the island of Rhodes.
Almost all of Helvis' 12 children were born to her while she was held prisoner.
In 1385, after negotiations and many ruinous concessions to the Genoese, they were released and James was crowned king.
In 1393, she became Queen of Armenia.
John I, Duke of Brunswick-Grubenhagen
John I, Duke of Brunswick- Grubenhagen( born: before 1322; died: 23 May 1367) was provost of the St. Alexandri Minster in Einbeck.
He was the son of Duke Henry I" the Marvelous" of Brunswick- Grubenhagen and his wife Agnes of Meissen, daughter of Margrave Albert II of Meissen.
James I of Cyprus
James I (1334 – September 9, 1398) was the youngest son of King Hugh IV of Cyprus and by 1369 held the title "Constable of Jerusalem.
" When his nephew Peter II died in 1382, James became King of Cyprus.
James was also titular King of Armenian Cilicia and Jerusalem 1382–1398.
James was the third son of Hugh IV of Cyprus and his second wife, Alix of Ibelin.
His older half-brother was Guy, Prince of Galilee (1320–43), and his two brothers were Peter I, King of Cyprus (1328-1369), and John of Lusignan, Prince of Antioch (1329-1375).
Before becoming king, James had other offices and was known for his resistance against the Genoese invasion of Cyprus.

Question: Who is Helvis Of Brunswick-Grubenhagen's mother-in-law?
Answer: Alix of Ibelin