Dale, The accession information for Castle Kennedy (DFIC 153) at the NCGR states:
"Accession was collected. Scotland, United Kingdom.
Comment: Old variety from Scotland, but how it came to be in Scotland, possibly since the late 1700's, is unknown."
So it may be the same as what Condit describes or not. A couple of things I've seen from Todd Kennedy, who donated it to the NCGR in 1988, suggest it is distinct from Brunswick. Another part of Condit's section on Castle Kennedy from the 1955 Hilgardia publication states:
A color illustration of Ficus carica kennedyensis Hort. is given in L’Illustration
Horticole, vol. 13 (ser. 2, vol. 3), pl. 476. 1866. A writer in the Gardener’s Chronicle,
November 19, 1864, observed that Messrs. Lawson and Son were to distribute the Castle
Kennedy fig, which had been exhibited in Scotland and had obtained an award from
the Edinburgh Horticultural Society. An anonymous account in 1865 (Florist and
Pomologist, p.141) stated that this variety had then existed at Castle Kennedy for nearly
a century; but how it came there or what was its origin were matters on which there
was no reliable information. It was believed to be quite distinct from any other variety
in cultivation in England. Archibald Fowler, who grew this fig at Castle Kennedy,
along with Brunswick and Brown Turkey, also maintained that it was distinct from both
varieties. Several reports indicate that the trees are poor producers; but on the contrary,
Hogg stated, “The tree is an abundant bearer.” A writer of 1873, signed simply as “K.,”
reported that Castle Kennedy was worthless as a cropper.....it is a runaway, unfruitful
variety, not worth house room.” Brotherston noted that in England only one crop,
presumably the first, is produced in a year. This seems to confirm the report of Burger
and De Wet, that in South Africa the second crop requires caprification, a fact that
places the variety in the San Pedro group.
A letter dated June 20, 1954, from Sir John Dalrymple, Earl of Stair, states that two
trees of the Castle Kennedy fig are still being grown mainly for sentimental reasons at
Lochinch Castle, Stranraer, Wigtownshire, Scotland. R. W. Rye, the head gardener,
agrees with “K.” above that this fig “is not worth house room as it is very shy in setting
fruit.”
That also suggests that Castle Kennedy is distinct, but raises questions about its quality. Once again, I have no direct experience with this cultivar. Others probably know better than me, but it seems there is a fair chance this fig is pretty cold tolerant. That area of Scotland gets miserably cold. I think some of the folks on this forum have tasted this fig at one of the fall tasting parties at Wolfskill Orchard. So, some opinions about its quality might be available here too. I am hoping that forum members that have experience with cold tolerant cultivars will chime-in.
Good luck with your trees!