She was descended from the famous Munro clan, from Moray, despite the alternative spelling of her surname.
Experts have even pinpointed the small village where her forefathers came from - Edinkillie, near Forres.
The blonde bombshell was born Norma Jeane Mortenson in 1926, but took her screen name from her mother, Gladys Monroe.
Hundreds of members of Clan Munro will hear details of her Scottish kin during a clan gathering in the Highlands next weekend.
They will meet at Foulis Castle, near Dingwall, for an update on the latest discoveries in the clan’s DNA project.
Two years ago the project made an appeal for clan members to help to confirm the Scots origin of Monroe’s ancestors.
Monroe’s mother Gladys could trace her father’s line back to John Munro, a prisoner of war exiled to America after the Battle of Worcester during the English Civil War in 1651.
No Munro men who shared the same signature pattern of the male Y chromosome had been found in Scotland, so the link to the Highland clan was uncertain.
Now, the Clan Munro DNA project has finally proved that Marilyn’s forefathers were related to a Munro family from the Moray village of Edinkillie, near Forres.
Descendants of this Munro family, some of whom emigrated to the Bahamas in the 18th Century, carry the unique Y chromosome marker previously found only in descendants of exiled John Munro.
Another member of the Moray family, William Munro, emigrated from Scotland to Batavia, now Jakarta in Indonesia, in the early 19th Century.
He married into a Dutch family, and William’s descendant Roelof Zeijdel said: “I was most proud to discover my clan Munro heritage, but very amazed that DNA could show also I was related to this big star that everybody knows.”
Previously the Munro DNA project found that US President James Monroe was of a different male line, most closely related to the Munros of Teaninich Castle in Alness.
Clan chief Hector Munro said: “At Foulis Castle, Munros whose ancestors travelled throughout the world, as well as those who stayed in Scotland, will be coming together to celebrate our shared history, heritage and traditions, whatever their genes may tell us.”