Dany/Stannis/Euron: An Interesting Connection (Spoilers Extended)

"Bloodmagic is the darkest kind of sorcery. Some say it is the most powerful as well." -AFFC, Cersei VIII

and:

Melisandre put her hand on the king's arm. "The Lord of Light cherishes the innocent. There is no sacrifice more precious. From his king's blood and his untainted fire, a dragon shall be born." -ASOS, Davos V

Like Azor Ahai, by the likely end of The Winds of Winter, it is likely that numerous of our major character will have sacrificed their own children in order to further their goals:

Daenerys

"The grave casts long shadows, Iron Lord," Mirri said. "Long and dark, and in the end no light can hold them back."

Ser Jorah had killed her son, Dany knew. He had done what he did for love and loyalty, yet he had carried her into a place no living man should go and fed her baby to the darkness. He knew it too; the grey face, the hollow eyes, the limp. "The shadows have touched you too, Ser Jorah," she told him. The knight made no reply. Dany turned to the godswife. "You warned me that only death could pay for life. I thought you meant the horse."

"No," Mirri Maz Duur said. "That was a lie you told yourself. You knew the price."

Had she? Had she? If I look back I am lost. "The price was paid," Dany said. "The horse, my child, Quaro and Qotho, Haggo and Cohollo. The price was paid and paid and paid." She rose from her cushions. "Where is Khal Drogo? Show him to me, godswife, maegi, bloodmage, whatever you are. Show me Khal Drogo. Show me what I bought with my son's life."

...

Dany gestured at Ser Jorah and the others. "Leave us. I would speak with this maegi alone." Mormont and the Dothraki withdrew. "You knew," Dany said when they were gone. She ached, inside and out, but her fury gave her strength. "You knew what I was buying, and you knew the price, and yet you let me pay it." -AGOT, Daenerys IX

Stannis

No guarantee that it will happen in TWOW, but we know that Stannis is going to be the one to burn Shireen:

It wasn't easy for me. I didn't want to give away my books. It's not easy to talk about the end of my books. Every character has a different end. I told them who would be on the Iron Throne, and I told them some big twists like Hodor and 'hold the door,' and Stannis's decision to burn his daughter. We didn't get to everybody by any means. Especially the minor characters, who may have very different endings." -SSM, Screenrant Article: 10 October 2020

If interested: The Cost: Stannis' Ultimate Sacrifice

Euron

If you haven't read the Forsaken, please do. Euron seems to be planning a giant blood sacrifice/summoning.

The last we see of the Silence it has Aeron Greyjoy, Falia Flowers and Euron's son lashed to the prow:

He beckoned, and two of his bastard sons dragged the woman forward and bound her to the prow on the other side of the figurehead. Naked as the mouthless maiden, her smooth belly just beginning to swell with the child she was carrying, her cheeks red with tears, she did not struggle as the boys tightened her bonds. Her hair hung down in front of her face, but Aeron knew her all the same.

“Falia Flowers,” he called. “Have courage, girl! All this will be over soon, and we will feast together in the Drowned God’s watery halls.”

The girl raised up her head, but made no answer. She has no tongue to answer with, the Damphair knew. -TWOW, The Forsaken

Its also possible numerous of his other bastards could die as well:

He saw the longships of the Ironborn adrift and burning on a boiling blood-red sea.

We could also see this potentially happening at the Tragedy of Summerhall, as well as the Children of the Forest:

And so they did, gathering in their hundreds (some say on the Isle of Faces), and calling on their old gods with song and prayer and grisly sacrifice (a thousand captive men were fed to the weirwood, one version of the tale goes, whilst another claims the children used the blood of their own young). And the old gods stirred, and giants awoke in the earth, and all of Westeros shook and trembled. Great cracks appeared in the earth, and hills and mountains collapsed and were swallowed up. And then the seas came rushing in, and the Arm of Dorne was broken and shattered by the force of the water, until only a few bare rocky islands remained above the waves. The Summer Sea joined the narrow sea, and the bridge between Essos and Westeros vanished for all time. -TWOIAF, Dorne: The Breaking

TLDR: Each of these characters have/will become kinslayers/child sacrificers to try to achieve their goals. Each one will/have done so to try and hatch/summon a dragon or other beast.