Very interesting list of information on the remarriages of widowers. In the end, Princess Pilar (who wrote a book about her Spanish cousin) died unmarried: I'm not sure if she was ever linked to anybody.
That the two wives of the same man would be related in some way is no surprise: until World War I -- and for a good time afterward -- royals were expected to marry their own kind. So in a broad sense, they're all cousins. In particular, there are also plenty of cases where the two wives were first cousins.
As for Infante Don Carlos of Spain: in the end, he remarried with Princess Louise of Orléans, a second cousin of his first wife, Infanta Maria de las Mercedes. Interestingly enough, she was the same age as Infanta Maria Teresa, his former sister-in-law.
The reason for my asking is that an aunt is often thought of as somebody who would make a good stepmother to children born of a previous marriage. Surely there would have been a bond between Maria Teresa and her motherless niece and nephew. That's why I wondered if anybody suggested that she become the second wife of her widowed brother-in-law.
He certainly was a handsome man, with the ability to turn all heads -- far more attractive than his former brother-in-law, King Alfonso XIII. What exactly Princess Pilar of Bavaria saw in him is beyond me ...
It's conceivable that his former sister-in-law might have set her cap for him. But in the end, she married Pilar's brother Ferdinand, despite the fact that as of 1906, Carlos was still available on the marriage market. And it has been said that Louise made a decent stepmother to her stepchildren.
Apparently Pss Pilar had a crush for Alfonso XIII which was not reciprocated.
A.XIII married V-Eugenie of Battenberg in May 1906 when Pilar was barely 15 so not a prospective bride.
Correct me if I am wrong but I don't think she was even part of the list of prospective brides the spaniards were called to vote for.
As for widowers marrying sisters-in-law, you are right.
When D.Manuel succeeded to the throne, the Catholic Kings offered him the hand of Infanta Maria.
D.Manuel refused and asked for Maria's sister Isabel hand.
D.Manuel knew Infanta Isabel for ages.
Both had been confined at D.Manuel's mother palace after the Terçarias de Moura treaty together with Isabel's future husband D.Afonso.
D.Manuel was one year older than Isabel who was 5 years older than D.Afonso.
D.Manuel supposedely fell in love with Isabel during the Terçarias (1481-83) and the enfatuation continued while she was briefly married to his nephew Infante D.Afonso who died after a horsefall.
Naturally D.Manuel kept his feelings in secrecy during D.João II's reign.
Any move towards the King's daughter-in-law would have been considered lèse-Majesté treason and D.Manuel knew the King (his 1st cousin and brother-in-law) was not someone to be aggravated.
D.Manuel still remembered that D.João had murdered personally his elder brother D.Diogo Duke of Viseu.
After D.João II's death and his accession to the throne, D.Manuel naturally asked for Isabel's hand.
As the Infanta showed no interest in remarrying, the Catholic Kings offered the hand of their 3rd daughter Maria, but D.Manuel insisted - it had to be Isabel and she was persuaded to marry him.
After her death in consequence of a difficult childbirth, wanting to preserve the peace in the peninsula, and avoid that D.Manuel would re-marry any other european princess, namely a french one, Maria was pushed again towards D.Manuel who accepted her.
True or legend, Maria is quoted to have said to D.Manuel that in the end of the day, the two were meant to be husband and wife, a subtle reference to the king's previous rejection of her.
Another case of a widower marrying his sister-in-law happened in the early 19th century.
Fernando VII's brother, Infante D.Carlos, had married his niece Infanta D.Maria Francisca of Bragança, mother of his 3 sons, the daughter of King D.João VI and Queen Carlota Joaquina of Spain, Carlos' sister.
When D.Maria Francisca died, D.Carlos married her elder sister, Infanta D.Maria Teresa.
When Queen D.Estefânia died of typhoid fever in 1859, her husband King D.Pedro V considered askinf for her sister´s hand Pss.Marie of Hohenzollern-Sigmaringen.
The Duke of H-Sigmaringen politely refused argueing that Pss.Marie was too young.
D.Pedro V survived Queen D.Estefânia for c. 2 years and died in 1861.
Pss.Marie of H-S ended up marrying Pr.Philippe of Belgium count of Flanders only in 1867.
A curious case, not envolving widowers.
King D.Afonso VI of Bragança (1643-83) was severely handicapped.
Even so, he succeeded his father King D.João IV first king of the Bragança dynasty.
D.Afonso VI was married to Pss.Maria Francisca Isabel of Savoy-Nemours in 1666.
But the Queen was so disgussed to her husband that shortly after the marriage, she locked herself in a convent and asked for the annullement of the wedding on the grounds that it had never been consumated.
Eventually Rome issued a decree anulling the marriage.
Two years later, in 1668, the Counsel of State deposed the king and appointed his brother infante D.Pedro as Regent.
D.Pedro, being a fine and able man, asked his sister-in-law in marriage, and, after obtaining Rome's dispensation, the two got married.
After their marriage, former Queen D.Maria Francisca assumed her husband's title as Princess-Regent although she kept all the honours due to a Queen.
When deposed King D.Afonso VI died in September 1683, D.Maria Francisca regained her title of Queen next to her second husband D.Pedro II, but she died just 3 months after he 1st husband so she could not enjoy her title for a long period.
Was she touted as a potential queen consort of King Alfonso XIII of Spain, a first cousin? If so, there would have been a double marriage between their families, since her brother Ferdinand married his sister Maria Teresa in 1906. That union was the third straight generation of intermarriages between the Bourbons and Wittelsbachs, since both his mother and paternal grandmother had been born Spanish princesses.
Speaking of which: was Infanta Maria Teresa ever thought of as a potential second wife to her widowed brother-in-law, Infante Don Carlos of Spain (born a prince of Bourbon-Two Sicilies)? Her older sister, Infanta Maria de las Mercedes, had died tragically of complications from childbirth in 1904.
After all, unlike the United Kingdom, which legalized the remarriage of a widower to a sister of his deceased wife only in 1907, Spain and Portugal have always allowed such unions. Otherwise, there would have been no way that Infanta Maria of Aragon (third daughter of the famous Catholic monarchs, Ferdinand and Isabella) could have married her widowed brother-in-law, King Manuel I of Portugal, after her oldest sister also died in childbirth.