The precontract (i.e. prior marriage) between Edward IV and Eleanor Butler, née Talbot, has long been a subject of debate, but what has not previously been claimed is that Edward and Eleanor were so closely related as to have been unable to make a valid marriage without a special dispensation from the Pope. Recently, however, a writer using the pen name of Latrodecta has claimed (https://ricardianloons.wordpress.com/2018/09/08/the-trial-that-should-have-happened-in-1483/#comment-454) that they shared a relationship within the prohibited degrees, viz. “3rd degree consanguinity, 3rd degree affinity”.
Latrodecta has identified this impediment as arising from Edward’s mother Cecily Neville being the first cousin of Maude Neville of Furnivall, the first wife of Eleanor’s father, John Talbot, 1st Earl of Shrewsbury, and the mother of Eleanor’s older half-siblings. The claim is apparently that – despite the relationship involving no blood tie between Edward and Eleanor – it counts as an impediment of both consanguinity and affinity because half-siblings are included in the prohibited degrees of kinship. The author further claims that “Corroboration can be found in the dispensation granted for the marriage of his son [i.e. Edward IV’s younger son] and her niece [i.e. Anne Mowbray] – the relationship between her sister [i.e. Elizabeth Talbot Duchess of Norfolk] and Edward would have been the same” (that is to say, the same as between Edward and Eleanor herself).
I shall return to these claims, but first it will be necessary to explain these two types of impediment, what they are and how they were calculated at the period under consideration.
Consanguinity and Affinity
Consanguinity and affinity are the chief types of relationship that, under canon law, can produce a diriment (nullifying) impediment to a marriage. Of these, consanguinity is the easiest to understand as it is a simple blood tie: where there is no common ancestor, there can be no impediment of consanguinity. Impediments of affinity arose in those days from sexual intercourse (now only from marriage). The two sexual partners were deemed to have become, as it were, ‘one flesh’. Latrodecta should therefore not have been the least bit surprised to have ‘seen a case where the bridegroom had to obtain a dispensation because he’d already slept with his future mother-in-law’.
It is a common, indeed almost ubiquitous, misconception amongst ordinary historians that the relationship thus formed barred the couple’s respective blood relatives from marrying each other, but this is not so. Prior to 1215, the impediment of affinity had, it is true, been slightly complicated by the rule that a person’s second partner contracted affinity not only with the consanguines of the spouse but also with his or her closest affines (i.e. their new step-kin); at no time, however, had any couple shared a relationship of affinity without one of them having had a prior sexual relationship to cause it; two virgins could never be each other’s affines. Hence, when St. Augustine asked of Pope Gregory: ‘Is it permissible for two brothers to marry two sisters, provided there be no blood ties between the families?’ the great pontiff had replied: ‘This is quite permissible.’ The rules had been further simplified by the Fourth Council of Lateran (1215 AD), which had abolished the impediment between certain blood relatives of a person’s two spouses. The unifying principle of the remaining impediments is encapsulated in the maxim affinitas non parit affinitatem (‘affinity does not beget affinity’).
By the 15th century, therefore, there were no longer any step relationships that created impediments other than those (such as stepfather and stepdaughter) that just happened to involve direct affinity. In fact, it was almost de rigueur at this period for a widow and widower to cement their own union with at least one marriage between the offspring of their former marriages.
In the late Middle Ages, both consanguinity and affinity created an impediment to marriage up to the level of third cousins (another rule brought in by the Fourth Lateran Council). The method of calculation in use at the time – the so-called Germanic method – is extremely simple to use.
Edward and Eleanor: Consanguinity
To check for an impediment of consanguinity, one simply draws up two direct-ancestry trees, one for each party to the proposed marriage, with the prospective bride/ groom at one end, their parents (1st-degree consanguines) in the next row, after them their grandparents (2nd-degree consanguines), then their great-grandparents (3rd-degree consanguines), and lastly their great-great-great-grandparents (4th degree consanguines). Then one stands back, looks for any names common to both trees and counts the generations from each partner up to the closest match in any given line. Most often, the common stock, as it is called, (stirps in Latin) will be a couple, but it can also be a single individual, as would occur if an ancestor had married twice and the bride was descended from one of those marriages and the groom from the other. This is what is meant, and all that is meant, by half-siblings counting in the same way as full siblings: the only relevant half-siblings are those who link the couple via their shared ancestor.
I have carried out this very exercise for Edward and Eleanor, highlighting any common ancestors in red. As can be seen, there are none.
Note that Maud Furnivall, identified in the above article as the route to the alleged 3rd-degree impediment, appears on neither Edward’s nor Eleanor’s table; this is because she was only a collateral relation of Edward and no blood relation of Eleanor at all.
Let us now turn to the assertion that the dispensation for Anne Mowbray and Richard of Shrewsbury corroborates this alleged 3rd-degree consanguinity. There are, I fear to say, two problems with this, one of them terminal. First (to be picky) the Anne Mowbray dispensation is for consanguinity in the 3rd and 4th degrees (i.e. one of them was 3 degrees removed from the common stock, and the other, 4 degrees), whereas an even 3rd-degree consanguinity between Edward and the Talbot sisters would have resulted in an even 4th-degree consanguinity between little Richard and Anne. But rather more seriously, Latrodecta has overlooked the salient fact that all children have two parents. As the following consanguinity chart for Richard Duke of York and Anne Mowbray clearly shows, they were indeed related in the 3rd and 4th degrees but Anne’s relationship to Edward’s family lay on her father’s side and in no way involved her Talbot ancestry.
Edward and Eleanor: Affinity
Now let us turn to affinity. By sexual union, the consanguines of the one partner become the affines of the other. So, for instance, if Harry’s previous partner was Sally’s second cousin, then Harry and Sally would be related by affinity in the 3rd degrees. The check for affinity therefore works on the same principle as for consanguinity, except that the bride/groom needs to compare her/his consanguinity tree with that of the prospective spouse’s previous partner(s). This exercise I have carried out for Edward and Eleanor by drawing up this chart showing Sir Thomas Butler’s ancestry. Unfortunately Thomas’s chart is not complete in all areas, and not 100% verified in others, because much of his ancestry is relatively humble and not recorded, but it is highly unlikely that any of these obscure Cheshire ancestors would feature on the table of Edward of March. In short, there was no affinity between them either.
There was no relationship preventing Edward Plantagenet and Eleanor Butler from marrying each other. Readers do not need to take my word for this: there are plenty of sources available online that set out the different prohibitions and methods of calculating degrees of relationship in use by the Catholic Church at different periods. To be sure one has the correct understanding, all that is needed is to perform a few test calculations on couples whose ancestry and marriage dispensations are both known. Or some may wish to begin, as Edward IV’s councillors must have done in 1464, by checking for (non-existent) common ancestors on the trees of Edward IV, Elizabeth Woodville and Sir John Grey.
 The impediment of affinity arising from extramarital relationships was also to be gradually abolished. The first step was taken in the 16th century by the Council of Trent, which limited its effect to the 2nd degree (first cousins), but it was not until 1917 that this impediment was wholly confined to the consanguines of previous spouses.
 The most notable recent intrusion of this error into late-fifteenth-century English history is Michael Hicks’ claim that Clarence’s marriage to Isabel Neville prohibited Richard’s marriage to Isabel’s sister.
 Mary O’Regan, ‘Marriage Dispensations According to St Augustine’, Ricardian Bulletin, Autumn 2008, pp. 34-35.
 https://sourcebooks.fordham.edu/basis/lateran4.asp, canon 50.
 Thomas de Charmes, Theologica Universa ad Usum Sacræ Theologiæ Canditatorum, vol. 7 (1765), p. 357.
 https://sourcebooks.fordham.edu/basis/lateran4.asp, canon 50.
 A particularly clear explanation is given in the 1917 Catholic Encyclopaedia under ‘Consanguinity (in Canon Law)’: ‘Mode of Calculation’ (https://www.newadvent.org/cathen/04264a.htm).
 ‘Dispensation . . . notwithstanding that they are related in the third and fourth degrees of kindred’ (Calendar of Papal Register Relating to Great Britain and Ireland, ed. J. A. Twemlow, vol. 13 [London, 1955], p. 236).
 Again, The Catholic Encyclopaedia gives a useful summary under ‘Affinity (in Canon Law)’ (https://www.newadvent.org/cathen/01178a.htm).