The information on this page was taken from Harvey Green's website.

First Generation

William of Douglas

According to "The Black Douglas'" p68 above, William of Douglas is the "first of [the Douglas name] any certain record has been found]". He is thought to have been born in or before 1174. "He held lands at Douglas (said to mean 'black water'), from which he took his surname. William was surely related to [probably brother-in-law] Freskin the Fleming, who came to Scotland before the end of the reign of David I." It is believed that both William of Douglas and Freskin the Fleming came with their families from Flanders, "perhaps connected with the House of Boulogne."
Other than the possible connection with the Fleming, the wife of William of Douglas is unknown. He did however have one known son:
Second Generation
Archibald of Douglas who was given lands at Hermiston, in Lothian. William of Douglas died in 1213. No burial info is known.

Archibald of Douglas

Archibald of Douglas was born sometime prior to 1198. Archibald of Douglas died c1240. While marriages are unknown, he had two known sons:

Sir William of Douglas
Sir Andrew of Douglas, Ancestor of the Douglases of Morton

Third Generation

Sir William "Longleg" Douglas

Sir William of Douglas, known as "Longleg", was born c1200. Why or how he got the name 'Longleg' is unknown to me. Sir William "Longleg" died sometime after 1274. He had two known sons:
William "le Hardi" Douglas
Hugh of Douglas

Fourth Generation

Sir William "le Hardi" Douglas
Sir William "le Hardi" of Douglas was born c1240, but where the name "le Hardi" came from is unknown. He first married Elizabeth Stewart, and later married Eleanor de Louvaine. I have one child by each, and one unsure:
child by Elizabeth Stewart
James "the Good" (Lord of Douglas) child by Eleanor de Louvaine
Sir Archibald of Douglas child probably by Elanor de Louvaine
Hugh Douglas (Lord of Douglas)
William "le Hardi" died 1298 in a London prison.

Fifth Generation

Sir Archibald Douglas
Sir Archibald Douglas was born c1297. He married in c1328 to Beatrice Lindsay, and they had two known children:
Eleanor Douglas
William of Douglas
Sir Archibald of Douglas defeated Edward de Baliol, King of Scotland, in 1332 and was appointed Regent of Scotland during the minority of King David II. He was killed (unknown how) on 19 July 1333.

Sixth Generation

William of Douglas
William of Douglas, 1st Earl of Douglas, was born c1323. His first marriage was to Margaret, Countess of Mar (dau of Donald, 8th Earl of Mar). Whether through death, affair, or divorce, either before or after Margaret of Mar, he was also associated with and possibly married to Margaret Stewart. He also had at least one other child at some point either by marriage or affair.
children by Margaret of Mar
James Douglas of Drumlanring
unknown (m. Alexander Montgomerie)
(children by Margaret Stewart)
George Douglas
children by Unknown
Margaret Douglas (m. Sir Herbert Herries)
Margaret Stewart later (c1368) married Thomas of Mar.
William, 1st Earl of Douglas, died May 1384.

Seventh Generation

George Douglas
George Douglas, 1st Earl of Angus, was born c1376. He married on 24 May 1387 to Lady Mary Stewart, (daughter of King Robert III of Scotland). They had three children:
Elizabeth Douglas (b. c1397; m. Alexander Forbes)
William Douglas
Mary Douglas (m. Sir David Hay [1421/34-by 1Mar1478]; son:)
John Hay (1st Lord Hay of Yester)
George, 1st Earl, is said to have died of the Plague sometime after 04 September 1402 in England. After his death, Lady Mary remarried several times.

Eighth Generation

Sir William Douglas

Sir William Douglas, 2nd Earl of Angus, was born c1399. Sir William Douglas died Oct1437. In 1425 he married Margaret Hay and had two children:
George Douglas
Helen Douglas (m. by 1460 William Graham [c1448-1472])

Ninth Generation

George Douglas
George Douglas, 4th Earl of Angus, was born aft 1425. George, 4th Earl, died 14Nov1462 and is buried at Abernethy. He was married Isabel Sibbald, and they had two known children:
Archibald Douglas.
Jane Douglas (m. David "the Younger" Scott who d. 1492)

Tenth Generation

Archibald Douglas
Archibald Douglas was born c1454, and was the 5th Earl of Angus. He married on 04Mar1467/8 to Elizabeth Boyd; she died prior to 21 Feb 1497, and he is believed to have remarried, but unknown to whom. Archibald Douglas died sometime before 31January1513/4.
 They had three children:
George Douglas
Sir William Douglas
Lady Majory Douglas (b. aft 1467/8; m. Cuthbert Cunningham)

Eleventh Generation

George Douglas
George Douglas, Master of Angus, was born c1469. George, Master of Angus died 09 Sep 1513 during the Battle of Flodden Field. He was married by March of 1487/8 to Elizabeth Drummond (b. c1460), and I show five children:
Alison Douglas.
Archibald Douglas (6th Earl of Angus; b. aft 1488; m1. Margaret Hepburn, affair w/ __?__ Stewart; m2. Pss Margaret Tudor; m3. Margaret Maxwell; total two dau.)
Elizabeth Douglas (b. c1489; m. John Hay)
George Douglas (c1490-Aug1522; m. Elizabeth (Isabella) Douglas)
Janet Douglas (c1495-17Jul1537; m. John Lyon)

Twelfth Generation

Alison Isabella Douglas
Alison Isabella Douglas was born sometime after 1487. She married David Hume, 4th Baron of Wedderburne. The only child I know is

David Hume, 5th Baron of Wedderburne.