Just a drabble to explain my favourite pairings in the show. Based on the 2k3 series. Also, this laptop doesn't have a spellchecker, so appologies for any mistakes.

Splinter watched the steam rising up from his tea, coiling and curling in on itself as it faded from view once it was high enough. The delicate wisps that swept to and fro gave him the perfect focus to concentrate on whilst preparing to meditade, letting his mind wander as free as the steam. But today, he found he could do little to concentrate, seeing, but not taking in the elegent dance that usually gave him a strong sensation of peace.

With a short sigh, he rose to his feet, lightly gasping his walking stick as he glanced towards the door seperating his room from the lair as a whole. He knew why he found it so difficult to meditate lately. On a concious level he had expected it, embraced it even. After all, the happiness of his sons meant the world to the aged rat, even if the reason for this happiness wasn't quite something he had foreseen when he was raising them all those years. It left him with a bittersweet realisation however.

His sons were growing up.

With a short sigh Splinter rested his hand on the door, thinking that some of his stories would allow him to put his mind at ease when his ears flicked slighty. Soft murmering voices and the occassional chuckle came from the main living area of their lair. His sons were never so quiet when they were together, needing something to mentally, or physically stimulate them, either through thier hobbies or sparring. He smiled sadly to himself as he slowly eased the door open, peering out, confirming his suspicions.

Leonardo was sitting at the kitchen table, a pot of tea resting between him and his guest, both of them talking quietly, but animatedly, hands moving in vivid gestures as they made their points to each other. Opposite him, the ronin Usagi Miyamoto was chuckling at a joke or memory the blue clad turtle had relayed to him, sipping from his own cup of tea. Both pairs of Katana were laid on the table, too far away to reach should the other attempt something. A trust that Leonardo rarely afforded anyone not outside their immediete family.
Splinter let his eyes roam over his eldest son's fom, giving a short smile. His shoulders were less tense, a smile coming far more easier to his face than before. Usagi was good for him, allowing him to relax and encouraged him to take time for himself rather than constant training. Usagi himself benefited from their relationship also, his life as a wandering samurai was one of constant movement and struggles, adapting form one situation to the next. Leonardo and his home that was always open to him, gave him a much needed anchor. A constant in a world of shifting alligences and battles.
He admited to himself that he was shocked when Leonardo came to his room and stated, quite calmly, thast he was in a relationship with the rabbit samurai. He appeared so composed, but he could see the various twitching muscles that betrayed his anxiety. His need for his father's approval. Once he saw how happy the pair of them were, he gave them his blessing, though he still had to wonder when exactly the pair had moved from being mere friends to something greater.

Michealangelo was over in the corner, his usual energy being subdued by the presence of the other, more calmer individual. Carefully twisting his ears, Splinter could make out hushed tones about subjects he knew his other sons would find difficult to believe that their youngest would even think about, much less debate and discuss it. The orangle clad ninja had a deep philisophical mind. Wrapped in an immature, childish personality perhaps, But he did think more about the world and its inhabitants than he led his brothers to believe. He had long ago accepted the role of "Jester" in their family, brightening up their days whenever it got truely dark.
Of course, these days his brothers had others in their lives to comfort and entertain them, and so the carefully built shell was allowed to fall. He still kept up the childish persona around his family, and it hurt slightly knowing his youngest would never truely be himself around them, but he was comforted by the knowledge that someone was allowed to see beyond that, and allow Michealangelo to flourish.
He will admit however, the last person he had ever thought would end up with his son would be the giant Leatherhead, currently acting as both chair and blanket, tail and arms wrapped around him, holding him close to his chest. It did make sense however. Leatherhead needed a brighter outlook on life and Michealangelo had plenty of life to share. He never truely thought of others as monsters, no matter how awkward their inital meeting would be. He gave the alligator a sense of belonging and acceptance that he had not felt since the Utrons left earth and Splinter knew, without a doubt, that he would tear anything, anyone apart who dared threatened his young companion.
That did not stop the elderly rat from point-blank refusing to think about what happens when the two retired to Leatherhead's lair for a night.

Rapheal was always hot headed... So much so that Splinter allowed him certain indulgences that would bring about a swift repremand from either of his brothers, a fact he knew caused some friction between the two eldest. He held a great belief in justice and punishing those who deserve it that caused his blood to boil whenever he witnessed a crime or the guilty walking free to roam the streets to cause more trouble. It was the main cause of his anger, being stuck down here, in the dark and the damp, while those who commited such attrocities were allowed to roam the surface without fear.
Of course, since the Crimson ninja was given leave to journey to the surface, the criminal element of the city quickly learned to watch the sky for wrath to decend on them.
Which, really, shouldn't have made his current partner so surprising... Both of them held the same rage against crime and delivered swift punishment when they found it. But even now, Splinter just could not wrap his mind around what his eyes were telling him.
On the damaged sofa, watching a sport of some kind, Rapheal and Casey Jones were debating their favourite teams pros and cons with the aid of a few fists and headlocks.
Splinter had to wonder just how their relationship could have evolved from beating up scum together to... Well. As much as he would like not to, his ears heard a number of things. At least his brothers had the decency to leave the lair when they were... Occupied. He had half-suspected it was a spur of the moment thing. The heat of battle, the haze of bloodlust, the pounding of adreneline, all leading to the two clutching at each other. But here and now, in the quiet and calm, his old eyes could easily pick up on the affection and respect the two had for each other. And yes, perhaps a substantial amount of lust also.
Considering their rather few options when it came to pairing up, Splinter had to accept that his son could have done considerably worse.
Even so, they did benefit from their relationship. Their two fires that usually burned hard and fast and burnt all who came too close was now no less fierce, but much more controlled. Like two bushfires cancelling each other out, they eased and calmed each other, perhaps just with the knowledge that they were not alone in their vendetta against the injustice of the world.

Which brought Splinter to his last remaining son. Donatello, with a mind that Splinter knew vastly eclipsed his own, was by far the shyest, reserved and compassionate of his sons. That vast intellect that he dedicated to doing good by others often left him isolated, as no one in his family could even begin to comprehend the theories and musings that his active brain overflowed with. As the years went by, and his sons grew up, he noticed the amethyst brother becoming quieter and quieter, forgoing contact with his brothers or father in preferance to his own thoughts.
Which made the arrival of Donatello's current conversation partner a godsend. Someone who could not only keep up with his son's lightning fast mind, but even challange him to consider new thoughts and ideas, presenting him with alternative viewpoints that his singular outlook would not usually consider.
The change was apparant almost from day one, long before the two had gotten together. He was more eager to join his brothers, talked more, laughed more. It was as though a great weight had been lifted from his shell, and the once vibrant and sweet turtle tot he knew returned. He still had his moments, such as when he had to "dumb down" his explanations, something he knew exasperated his son to no end, but for the most part Donatello had returned to the family.
When April first came across their family, Splinter had been consumed with fear, anger and outright hostility. And though he would never condone harming an innocent such as Ms O'neill, he had far more experiance lurking in the shadows than his sons. If she had become a threat to his sons... She would have simply dissappeared.
Looking back now, Splinter was ashamed of himself, thankful none of his sons could read those complex emotions yet. April had become almost a daughter to her, training her in the styles and techniques that his sons, no matter their skill, could never master. Yes, while their shells were incredibly useful defensive features, they rather limited their flexibility. Something April had no problems with. And when Donatello glanced over at her training, he knew he had no problems with it either.

As Splinter watched his sons interact with their loved ones, he finally decided something had to be done, otherwise he'd never meditate again. Calling his sons towards him, he looked over the quartet kneeling before him before glancing up at the four who had completed their lives. With a short, hidden grin, he clasped his hands behind his back as he called forth Donatello.
"My son... I believe it is time to talk to you about something of the greatest importance..."
The purple ninja sat straighter, a determined glint in his eyes. Pacing back and forth, the rat snapped his tail in agitation.
"While I have no problems with your brother's choices in life, this is without a doubt something that I can only entrust to you."
With his back turned to the lair, Splinter could only imagine the looks on his son's faces, unable to hide his grin this time. Even he had to indulge himself in some mischeif now and then.
"Quite frankly..."
He turned, grasping Donatello's shoulders with both hands, looking him straight in the eyes.

"You are my only hope for grandchildren my son. I fully intend to be kept advised on any changes that may happen with you and Ms. O'neill..."

Inwardly the rat grinned as he watched the scandelised looks on his sons, their boyfriends and April's deep blush.

So there we go. I know not everone will agree with my pairings, but that's cool. Why not drop me a comment explaining why you think a certain pairing would/would not work? Thanks for reading!