From these clues, draw a family tree depicting each of the 12
person's exact relationship to Nathan.  (You may need to add
one or more unnamed ancestors to link all 12 to Nathan.)

Clue 1:  The 12 people include five women (Sabina, Tamar,
Ursule, Valpurga, and Wilmot).  Their husbands were Aella,
Benno, Cadelon, Donogh and Gregor, in some order.

Clue 2:  The 12 people include seven men (five just mentioned,
and Ephraim and Fjolnar).  Each had children only by a single
lawful wife.  Each of these seven wives had children only by
a single lawful husband who was not her own father, brother,
son or nephew.

Clue 3:  Three of the men did not have any brothers.  Aella was
Donogh's brother.  Gregor was the brother of the seventh man.
(These are full-brothers, not half-brothers.)

Clue 4:  Ursule is Fjolnar's granddaughter.
Neither Sabina nor Wilmot is descended from Fjolnar.

Clue 5:  Ephraim had no daughters.  His grandchildren included
at least three of the 12 people.

Clue 6:  The set of 12 includes both parents of Nathan,
all of his grandparents, and all of his great-grandparents.
The set includes exactly three of Nathan's great-great grandparents.

Clue 7:  Valpurga was Tamar's mother and Wilmot's daughter.
Aella was Benno's father.

Comments:
(1) I'm somewhat confident the puzzle has a unique correct
solution.  Money-back guarantee.  :-)

(2) FWIW, the pedigree is the actual official pedigree of a
19th-century King, though with names changed.

(3) You needn't use Ascii art to draw a family tree; the
Ahnenreihe system represents a pedigree with a list of
number-name pairs.

(4) This puzzle may be difficult but should be straightforward
and doable for someone with good grasp of kinship charting.

Dearest regards, James Dow Allen (mail address: jamesdowallen at gmail)

  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -  -

I'm sorry this puzzle attracted little interest.
Perhaps someone browsing the Google archives 50 years
from now will be intrigued by the puzzle, so I'll post a
SPOILER just to make the archives complete.

I'm afraid some readers dismissed the problem thinking it
might be tedious or ambiguous but, though difficult
perhaps, I think it was a fair, enjoyable problem.
Give it another try, before reading further.

Puzzle reposted as spoiler space....

This is the official pedigree of a 19th-century King.
I show those real names in parentheses.

Summary Ahnenreihe:
 1. Nathan    (Alphonso XII King of SPAIN)
 2. Benno     (Francisco de Asis BOURBON)
 3. Tamar     (Isabel II Queen of SPAIN & the Indies)
 4. Aella     (Francisco de Paula BOURBON)
 5. Ursule    (Louise BOURBON of the Two Sicilies)
 6. Donogh    (Ferdinand VII King of SPAIN & the Indies)
 7. Valpurge  (Cristina BOURBON of the Two Sicilies)
 8. Gregor    (Charles IV King of SPAIN)
 9. Sabina    (Marie-Louise of PARMA)
10. Cadelon   (Francis I BOURBON of the Two Sicilies)
11. Wilmot    (Isabel BOURBON)
12. same as 8
13. same as 9
14. same as 10
15. same as 11
16. NN        (Charles III King of SPAIN)
18. NN        (Felipe BOURBON Duke of Parma)
20. Fjolmar   (Ferdinando I King of SICILY)
22. same as 8
23. same as 9
32. Ephraim   (Philip V King of SPAIN)
36. same as 32
40. same as 16

Note that *everyone* in the puzzle is an agnatic descendant of
``Ephraim'' (King Philip V) and so is a BOURBON.  Don't worry that
King Alphonso XII was overly inbred, however.  His mother the
Queen enjoyed the company of several men, none of whom was her
impotent King Consort (though I'm told that when in Spain it's
impolite to suggest Alphonso wasn't the son of Francisco de Asis.)

Best Wishes,
James Dow Allen

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It attracted my interest, but I must admit I was struggling
to get a proper handle on it.

I will let you know if I do.

Regards

Matthew Newell