283AC, month unknown - The Tower of Joy
Lyanna screamed in pain.
The Kingsguard each furiously leafed through the literature Rheagar had left them with - be it "Midwifery for the not so bright", "Midwifery in Seven Easy Steps" or "Bun in the oven – how to deliver". Ser Gerold, coming as he did from the centre of learning as it was understood in Westeros, was the first to unearth a relevant passage. Relieved, the Bull shared his find with the others. Screaming was to be expected!
"You fucking useless cunts! I'll rip your balls off!"
Thankfully the information explaining that cursing was also part of the birthing process was in the next sentence; hence neither Ser Arthur nor Ser Oswell had to strain their mental facilities while browsing the august tomes for further knowledge.

* * *
A few hours, some screaming and much cursing later.
Ser Arthur – who had the most delicate hands of the trio – carefully dunked the infant in a bucket with tepid, clean water as to wash the yucky gunk off.
Then Lyanna's "gaping womanly mouth" – as the bards had it – with a bluish cord hanging out it - spewed forth a new cascade of liquid ...
"You dragon spittle licking pillow biters!"
And the process began anew ...

* * *
Half an hour, some screaming and much cursing later.
Ser Arthur – delegated to this duty as he had done it once before and thus was the most experienced of those present -– carefully dunked an infant in a bucket with discoloured water as to wash the yucky gunk off. Ser Gerold was vigorously rocking infant number one in a spirited endeavour to lull it to sleep. The newborn seemed keen on practicing its lungs, though. Ser Oswell – universally acclaimed for his raw physical power and rugged manliness - held up Lyanna's pert bottom with one hand while he tried to push a fresh bed sheet underneath her.
Then Lyanna's "entrance to her secret womanly core" – as the bards had it - with two bluish cords hanging out of it - spewed forth a new cascade of liquid ...
"Cocksucking flea ridden impotent shit eaters!"
And the process began anew ...

* * *
A quarter of an hour, some screaming and cursing later.
Ser Arthur – by now an expert and the Kingsguard's acknowledged authority on cleaning infants off their yucky birthing goo – carefully dunked an infant in a bucket with tepid and discoloured water. This time he remembered to reheat the water – he made a note to himself to change the water the next time too.
Ser Gerold – who had seen a nursing bitch in the kennels once – had tried to persuade the lady Lyanna to lay on her side to suckle. He was at a loss – however – to explain how was that to help with the feeding of two babies at the same time. Hence the young mother was reclining on the pillows, with one infant in the crook of each arm. One at each breast. She was eying number three with some worry in her slate grey eyes reminiscent of the Northern sky before a snowstorm when the wolves howl, the Wildlings prowl and the wind roars through the trees ...
Ser Oswell knelt in awe and mumbled a prayer of gratitude to the Father, Smith and the Crone – he served a genuinely Great Man!
"The dragon has three heads" – the Prince had said.
And here they were, before his eyes, just as had been foretold – three little Dragons!
"Rheagar is SOOO smart", the loyal knight sighed with admiration and a dash of envy.

* * *
Almost a year later, Winterfell.
Eddard Stark looked down, then to the side. He ground his big toe into the floor of the nursery.
"These ... these three babes are my bastards ... Jon, Jen and Jane ..."
Lady Catelyn fainted.
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AN:

I came across the idea (given out in a sort of "shits and giggles" sort of way) of Lyanna having triplets as to fulfill the prophecy and could not resist :D - hence inspiration for fic came from Javelin Catcher at the ASOIAF forum.

My research into multiple births - the things I do for fanfction! - showed that the "order of delivery" is baby-baby- afterbirth-afterbirth etc., and not baby-afterbirth-baby-afterbirth, as I had initially suspected.

Names suggested by Magicmoon111 at "the other" fanfic site :)

For those waiting for "Foremost the pack" updates - sorry, writer's block still :(