MACE TYRELL, Lord of Highgarden, Warden of the South, Defender of the Marches, and High Marshal of the Reach
—his wife, LADY ALERIE, of House Hightower of Oldtown,
—their children:

—WILLAS, their eldest son, heir to Highgarden,
—SER GARLAN, called THE GALLANT, their second son, newly raised to Lord of Brightwater,
—SER LORAS, the Knight of Flowers, their youngest son, a Sworn Brother of the Kingsguard, wounded on Dragonstone,
—MARGAERY, their daughter, twice wed and twice widowed,

—his widowed mother, LADY OLENNA of House Redwyne, called THE QUEEN OF THORNS

crazy-plushies-and-cats-girl replied to your post:

could you explain it please? i don’t see it…

So, in ASOS we learned that Olenna Redwyne was betrothed to a Targaryen prince as a child. Before TWOIAF was published, we didn’t know who Olenna was betrothed to or why, which led to a lot of (incorrect) speculation about Aegon V securing the Redwyne navy for the War of the Ninepenny Kings, and discussions of Aegon V as a military commander/political strategist etc

We later found out in TWOIAF that Olenna Tyrell was betrothed to Aegon V’s youngest son, Daeron Targaryen. The problem with the betrothal was, Daeron Targaryen was gay and had no interest in women. He loved Ser Jeremy Norridge, a knight from the Reach:

Though betrothed to Lady Olenna Redwyne of the Arbor when both of them were nine, Prince Daeron repudiated the match in 246 AC, when he was eighteen … though in his case, there appears to have been no other woman, for Daeron remained unwed throughout the remainder of his short life. A born soldier who rejoiced in tournament and battle, he preferred the companionship of Ser Jeremy Norridge, a dashing young knight who had been with the prince since the two of them were squires together at Highgarden. Prince Daeron brought to his father, Aegon, an altogether deeper sort of grief when he was killed in battle in 251 AC, leading an army against the Rat, the Hawk, and the Pig. Ser Jeremy died at his side, but the rebellion was quashed, and the rebels slain or hanged.

Olenna says in ASOS, “They tried to marry me to a Targaryen once, but I soon put an end to that” but as we see in TWOIAF, the last part isn’t true, at least according to Maester Yandel. Daeron refused to marry Olenna, instead of the other way around. I believe Olenna is probably trying to make herself look better in front of Sansa, who also had a prince cast her aside in favor of another. (But Sansa didn’t want to be married to Joffrey at that point, while I believe Olenna did want to marry a Targaryen prince, given her blasé attitude toward Luthor.) 

Olenna’s situation had some parallels to Margaery’s, but of course Renly Baratheon actually went through with his marriage to Margaery while continuing his relationship with Loras Tyrell. Which is interesting, because one of the first things readers hear from Olenna is that she disapproved of backing Renly’s bid for the throne, that she protested against Margaery becoming Renly’s queen:

The old woman turned back to Sansa. “It’s treason, I warned them, Robert has two sons, and Renly has an older brother, how can he possibly have any claim to that ugly iron chair? Tut-tut, says my son, don’t you want your sweetling to be queen?”

And so, Olenna says that Renly “knew how to dress and he knew how to smile and he knew how to bathe, and somehow he got the notion that this made him fit to be king. The Baratheons have always had some queer notions, to be sure. It comes from their Targaryen blood, I should think.” The word “queer” is defined as “strange” but it has another (sometimes pejorative) definition in that it refers to someone who is not heterosexual, or in Renly’s case, someone who is gay.

What Olenna’s saying is that Renly was gay just like his Targaryen great-uncle, like, the joke she’s making is that Renly inherited his gayness from Great-Uncle Daeron, that Baratheon homosexuality comes from their Targaryen side. (Some people speculate that half-brothers Aegon the Conqueror and Orys Baratheon were more than just friends btw, and well, I mean, if you’re already banging both your sisters, a half-brother might fit right in.) 

And what makes this so funny to me is that the fandom was obsessing over the line “they tried to marry me to a Targaryen once” and doing all of this intricate strategic and political analysis, when all along, GRRM put the reason for Olenna’s broken betrothal right there in the same paragraph, staring us all in the face when she references “queer notions”. Presumably GRRM had this planned since the late 90s, when he was first imagining Dunk & Egg and writing ASOS. It’s quite funny to me how the fandom tends to overanalyze things.

That ASOS scene where Sansa meets the Queen of Thorns can be looked at anew, when you think about parallels between Sansa and Olenna now, and Olenna/Daeron/Jeremy and Margaery/Renly/Loras.