Sinclair in Shetland
M.Sjostrom
traditional genealogies (such as Grant's 'County Families') have some chronological messes about Shetland Sinclairs in late 1500s.
The following is an outline of some desk analysis, how their lineages were, if chronological inconsistencies are corrected:
1 around-1630s-born children of the family of a laird of Quendale
2 Jon de Sinkler, laird of Quendale (fl 1628; d aft 1667; born est 1600)
m 1628
3 Barbara de Sinkler (fl 1628; born bef est 1610)
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4 Jep (/Jami) de Sinkler, laird of Quendale (fl 1610; d 21 sept 1647; born est 1570)
5 Barbara Stewart (d aft 1647; born est 1580s)
6 Adam de Sinkler, laird of Brew (fl 1597, 1602, 1611; d 1627; born in est 1560)
7 Elin Bruce (fl 1588; born after est 1560)
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8 Melkolm de Sinkler, laird of Quendale (fl 1565; d 6 Jan 1618; born est 1540)
9 Margret de Sinkler (born est 1550)
10 Jamie Stewart, laird of Graemsay
12 Jep (/Jami) de Sinkler, laird of Brew (d aft 1588; born est 1530s)
13 Janet Sinkler
14 Laurence Bruce, laird of Cultmalindie, castellan of Muness, grand foud of Shetland (born est 1535; d in Aug 1617)
15 Ealan Kennedy (fl 1559; born est 1540; dc 1568)
----
18 Heinrek de Sinkler, laird of Brugh (d 1575; born in est 1520) - probably son of: Edvard de Sinkler, laird of Brugh (d aft 1539; mentioned in c1529; born bef est 1500)
19 Katrina Kennedy (born est 1530)
20 Robert, earl of Orkney
and mistress
21 Janet Robertson of Struan
24 Olav de Sinkler, laird of Havera and Brew, grand foud of Shetland (fl c1529; mentioned in 1539; died after 1567; born bef est 1510)
25 Margret Baird
26 Laurence de Sinkler, laird of Sandes and Houss (fl 1560; born bef est 1500)
27 Janet Strang (died after 1560; born bef est 1520)
28 Iain Bruis, laird of Cultmalindie
29 Eupheme Elphinstoun
30 Alexander Kennedy, laird of Girvan Mains
----
48 Heinrek Sinkler, of Hevera (d 1545)
49 a daughter of: Viljalm de Sinkler, laird of Houss (d 1539; fl c1529) and presumably his wife, a noblewoman of the family of Sinkler of Dunbeath
50 Alexander Baird
M.Sjostrom
there seems to be a tradition (claim) that the Sinklars of Brugh, Shetland, descend from this Ingeborg Valdemarsdatter:
http://genealogics.org/getperson.php?personID=I00546245&tree=LEO
Ingeborg obviously was a young adult in 1379 - when her marriage with Jon de Sinkler apparently took place.
Sinklers of Brugh seem to appear to steadier documentation in early 1500s.
There is a century (three-to-four generations) [between Ingeborg and the first attested lairds of B. in 1500s] which cannot presumably be ascertained as to how the lineage went.
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On one hand, tenants in some stages of history took the surname of their masters - but it looks to me that in Shetland, surnames were not generally needed (consequently nor deliberately 'taken') in medieval era nor in several early modern centuries, since the patronymic system flourished at least to the 1700s.
In scandinavian culture mainly having patronymics as mainstream name system, the general pattern has been that if ones had a surname, it was an exception and usually due to proper inheritance of it from direct ancestors.
On the other hand, it is conceivable that the surname Sinkler (orig. Saint-Clair) came to late-medieval Shetland culture as hereditary byname of some families who were cadets of the Sinkler ruling dynasty of the islands.
The proliferation of that byname among men (and families) in the early 1500s when steadier documentation starts,
combined with the fact that apparently that name at that time was held by 'magnates' of Shetland, such several men who owned a manor or more,
can for most be presumed as outcome of branching of the dynasty's cadets in Shetland during the preceding century-and-half (1360s- early 1500s)
So, although their descents cannot apparently be proven,it is plausible that these Sinklar-bynamed magnates in early 1500s were direct descendants of the dynasty,
and its cadet branches
M.Sjostrom
in Tony Gott's collection about Shetland families, this same family's ancestry is as follows:
http://www.bayanne.info/Shetland/pedigree.php?personID=I15094&tree=bayanne_1&parentset=0&display=standard&generations=6