Arnold III Count Loon was born to Louis Loon I Count Loon and Agnes Metz Countess Loon.
Around 1134 [his father] Louis Loon I Count Loon (age 26) and [his mother] Agnes Metz Countess Loon (age 20) were married. She by marriage Countess Loon.
Around 1180 [his mother] Agnes Metz Countess Loon (age 66) died.
In 1206 Arnold III Count Loon and Adelaide Reginar (age 16) were married. She the daughter of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant (age 41) and Maud Metz (age 36). He the son of Louis Loon I Count Loon (age 98) and Agnes Metz Countess Loon. She a great x 3 granddaughter of King William "Conqueror" I of England.
In Jan 1206 Gerard III Count Guelders (age 21) and [his sister-in-law] Margaret Reginar Countess Guelders (age 14) were married. She the daughter of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant (age 41) and Maud Metz (age 36). He the son of Otto I Count Guelders (age 56) and Richardis Wittelsbach Countess Guelders (age 33). She a great x 3 granddaughter of King William "Conqueror" I of England. 
From 1207 to 1214 Arnold III Count Loon was held hostage in England in order to guarantee the obligations of his brother [his brother] Louis II and his wife Ada of Holland (age 19) to give up the county of Holland.
In 1212 Henry Welf VI Count Palatine of the Rhine (age 15) and [his sister-in-law] Mathilde Reginar Countess Holland and Palatine (age 12) were married. She by marriage Countess Palatine of the Rhine. She the daughter of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant (age 47) and Maud Metz. They were third cousin once removed. He a great grandson of King Henry "Curtmantle" II of England. She a great x 3 granddaughter of King William "Conqueror" I of England.
On 06 Dec 1214 Floris Gerulfing IV Count Holland (age 4) and [his sister-in-law] Mathilde Reginar Countess Holland and Palatine (age 14) were married. She by marriage Countess Holland. She the daughter of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant (age 49) and Maud Metz. He the son of William Gerulfing I Count Holland (age 47) and Adelaide Guelders Countess Holland. They were half third cousin once removed. She a great x 3 granddaughter of King William "Conqueror" I of England.
On 02 Aug 1218 [his brother] Henry Count Loon (age 82) was fatally poisoned a few days after his [his brother] brother had been. His brother Arnold III Count Loon succeeded III Count Loon.
In 1220 William Gerulfing I Count Holland (age 53) and [his sister-in-law] Marie Reginar Countess Holland (age 30) were married. She by marriage Countess Holland. The difference in their ages was 23 years. She the daughter of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant (age 55) and Maud Metz. He the son of Floris Gerulfing III Count Holland and Ada Dunkeld Countess Holland. They were half third cousins. She a great x 3 granddaughter of King William "Conqueror" I of England. 
In 1221 Arnold III Count Loon died.
After 1221 William Auvergne X Count Auvergne (age 29) and [his wife] Adelaide Reginar (age 31) were married. She the daughter of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant (age 56) and Maud Metz. She a great x 3 granddaughter of King William "Conqueror" I of England.
Godfrey Reginar and Marie van Oudenaarde were married. He the son of Henry Reginar VIII Duke Lower Lorraine I Duke Brabant and Maud Metz. He a great x 3 grandson of King William "Conqueror" I of England.
Maternal Family Tree: Arnold III Count Loon
Father: Louis Loon I Count Loon
GrandFather: Folmar V Count Metz
Mother: Agnes Metz Countess Loon