Yes...Spanish and Portuguese mistresses...
Most Portuguese kings had mistress and left illegitimate children.
Start with D.Afonso Henriques and scroll down the dynasties.
http://genealogia.netopia.pt/pessoas/pes_show.php?id=1His son D.Sancho I was known as “O Povoador” (The Populator).
He contributed a lot ;Dwith some +/- 20 sons between legitimate and illegitimate.
On the 1st dynasty, D.Pedro left the most famous.
His sons with Inês de Castro, and the son he had with Teresa Lourenço, later King D.João I.
D.João I also had a very famous illegitimate son, D.Afonso, founder of the Bragança family who would reign in the 17th century.
D.João II had an illegitimate son D.Jorge .
After the death of D.João's own son, Infante D.Afonso, he tried to legitimize D.Jorge and make him his successor, which cause the anger >:(of Queen D.Leonor (whose brother was next-in-line to the throne

). This may have caused the death of the king by poisoning :-/.
With the Braganças, the tradition was renewed with D.João IV and D.Pedro II.
D.Pedro did all he could to steal his brother’s wife

(and his crown), but when he achieved his purposes he neglected her (his wife, not the crown

) and had lots of mistresses.
The most noble House of Lafões is issued from his liaision with Ana Armanda du Vergé, a French lady-in-waiting of the Queen.
Another of his Mistresses was known as Flor da Murta, the Flower of the Myrtle.
D.Pedro’s son D.João V choose most of his mistresses among the nuns

mainly at Odivelas convent. He left at least 3 sons, known as the “Meninos de Palhavã” (little boys of Palhavã) as they were raised at the Palhavã Palace – nowadays the residence of the Spanish Ambassador
http://www.embaixadadeespanha.com/.
There are no acknowledged sons of King D.José but he certainly had lots of mistresses.
He was returning from a pleasure night with one of his mistresses

(of the family of the marquesses of Távora) when he was shot and wounded

allegedely by servants of the duke of Aveiro.
This almost regicide gave the PM Marquess of Pombal the justification to anilihate the rebel nobility whose heads were the Távoras and the Duke of Aveiro, a descendant of D.Jorge (ill.son of king D.João II).
D.João VI was an awkward and difficult king :-/.
He had an affair with the grand-daughter of the Marquess of Marialva (a rape would qualify it better

),
http://genealogia.netopia.pt/pessoas/pes_show.php?id=108941, a daughter was born, he hastly married the mother with the court doctor and banished them from Court, never recognizing his daughter. His wife Carlota Joaquina, also had a legion of lovers, and her last sons were not D.João’s

.
The mistresses of D.Pedro have already been treated so I’ll speak of the younger sons of D.João.
Infanta D.Isabel Maria’s wedding to the Prince of Condé was being negociated when the Princess told daddy that she was pregnant

. Naturally the French ambassador heard the story and the marriage was cancelled.
Apparently the father was a british officer with whom she had a second child.
Her brother D.Miguel also fathered a daughter from an unknown woman, but, given his character, he most probably had many more.
There is an excellent book “Paixões Reais” by Eduardo Nobre who deals with all those royal affairs.
There is of course the debate whether Elise Hensler's daughter was D.Fernando II's

.
D.Pedro V never had a mistress and when his beloved wife died

the authopsy revealed she was a virgin

.
His brother, D.Luis, the sailor-king, had lots of lovers, one of which the famous actress Rosa Damasceno with whom he had at least a son.
Then followed D.Carlos, who had lots of mistresses.
The last one's daughter caused a lot of embarrassment as she presented herself as Duchess of Bragança and heiress to the throne, naturally only after the death of King D.Manuel II

.
After loosing her case in court, she sold her “rights” to an infamous Italian

who claims to be the rightful heir to the throne and also a descendant of Infant D.Afonso and who distributes decorations and titles to his followers.