No, not that I found so far... would probably be too easy, right? ;)
I googled "Laurent Ducharme slave", and found the following:
Laurent Ducharme,, born Aug 10, 1723 in Montreal, Quebec; died Aft. 1787. He married Marguerite Metivier Nov 26, 1753 in Montreal, Quebec; died.
Notes for Laurent Ducharme:
* pg 373, sous Louis Ducharme et Marie Picard:
4. Laurent n et b 10-08-1723 Montreal.
Source Dictionary of Canadian Biography Online:
DUCHARME, LAURENT, fur trader, baptized 10 Aug 1723 at Montreal (Que), son of Louis Ducharme and Marie Picard; m 26 Nov 1753 Marguerite Metivier in Montreal, and they had at least three children, d after 1787.
Laurent Ducharme was born into a Montreal family that had extensive experience in the western fur trade, and in 1754 he embarked on a modest fur trading career around the western lakes. By 1758 Ducharme had moved his wife to the small, fortified, fur-trading village of Michilimackinac (Mackinaw City, Mich). His family lived in a house on Rue du Diable where a slave girl, Madeleine, assisted with the housekeeping.
In 1761 British soldiers came to garrison Michilimackinac, but they never gained the friendship of the local Ojibwas. In the spring of 1763 Ducharme learned of Indian intentions to attack the garrison at Michilimackinac, but when he warned Captain George Etherington of their plans, the commandant berated him and also threatened to send prisoner to Detroit the next person to tell such a tale. On 2 June 1763 Ducharme watched in horror as the Ojibwas, organized by Minweweh, surprised the garrison and killed or captured all the soldiers. Ducharme and the other French inhabitants were not harmed.
As a result of the uprising, trade in the Upper Lakes region was severely disrupted, but when peace returned Ducharme once again became an active participant. During the late 1760's and early 1770's he was licensed to take trade goods from Montreal to the interior. Most of his business centered at Michilimackinac, but in 1769 he traded at Milouaqui (Milwaukee, Wis) and in 1772 at both LaBaye (Green Bay) and Milouaqui.
When the American revolution began to trouble the Upper Lakes in 1777, Ducharme served as an informer at Milouaqui for Captain Arent Schuyler De Peyster, commanding officer at Michilimackinac. On 15 May he sent the alarming message that the Spanish were attempting to get the Potawatomi chief, Siginakee (called Letourneau or Blackbird), to incite the Indians in the upper Mississippi valley against the British. This is Ducharme's only recorded involvement in the war.
Concerned about the "profaneness and impiety" at Michilimackinac during these unsettled times, Ducharme joined with a number of other merchants in 1778 in petitioning Sir Guy Carleton to send a missionary to Michilimackinac. No regular missionary had resided there for nearly ten years. Many merchants pledged their financial support. Ducharme promised L18 per year, a modest sum indicating that he was not one of the wealthier traders.
Economic conditions were also unstable. To combat the uncertainty a number of merchatns, including Etienne Charles Campion and Ducharme, pooled their resources and in 1779 set up a general store at Michilimackinac for one year. Ducharme invested half a canoe load, worth L7,500, again a comparatively modest sum. At his time he is listed as a resident of Montreal. Apparently he lived there only part of the year and, like many other small traders, wintered among the Indains to obtain furs at better prices. One of his posts was on the Fond du Lac River in Wisconsin where he traded with the Winnebagos.
More About Laurent Ducharme:
Baptism: Aug 10, 1723, Montreal, Quebec
Occupation 1: 1754 - 1787, fur trader
Location 1: 1758, Michilimackinac
Occupation 2: 1777, informer at Milouaqui for Capt. Schulyler dePeyster
Location 2: 1779, Montreal, Quebec
Occupation 3: 1779, partnership in a general store at Michilimackinac
Cited: 1787, witnessed an election of church wardens, Ste. Anne, Mackinac Island
(1762)October 16:Michilimackinac, baptism, Rene Francois Bourassa, unknown Father and Madelaine, a slave of Laurent du Charme.
I thought I had found at least one other child born to Madeline, and now I cant find where that was.
The only other thing I can think of, is that if Laurent DuCharme wasnt Cuthbert's Grandfather, perhaps Laurent's Brother, Louis DuCharme was?
What I found when I googled Louis DuCharme:
b: Jan. 6 1717 Montreal, QC d: Aug. 1782 Longue-Point, Montreal, QC
Married in Jan. 2, 1747 Montreal, QC to Marie Francoise Jourdain-dit-Labrosse: b: Apr. 13, 1727 Montreal, QC
Son: Louis DuCharme married on Nov. 7, 1786 St. Francois Laval, QC to Angelique Marchand.
I'm not sure if they had any surviving sons named Jean Marie...?