Tricardy, Dicardy and Boo

The triplets’ real names were George, Alan and Robert, but they insisted on being called Tricardy, Dicardy and Boo. Together they were known as the Trilobites because they were just a little weird; small identical brothers with the same thoughts apparently inhabiting three bodies. One of them would start a sentence and another finish it. It could be quite spooky. Other parents were overheard suggesting they were probably Midwich Cuckoos, though not within earshot of their proud mother and father.
Tricardy was the oldest by 30 minutes, and then came a Dicardy, and lastly Boo, who only differed from his brothers by giggling a lot.
As they grew older (but not much larger), their birthdays became more problematic. Being identical, friends and relations were inclined to buy them exactly the same things. They should have known better and were always mortified by the way their gifts of soft toys, colouring books and Transformers were pushed into a cupboard and ignored. The boys much preferred to play with the building materials they somehow intimidated older friends to scavenge from skips for them. The influence the eight-year-olds had over other children was inexplicable to the adults who wondered what they were building. 
Tricardy, Dicardy and Boo spent all their spare time at the bottom of the garden constructing, what their parents assumed to be, a portal to welcome the aliens they claimed would shortly invade Earth.
While everyone else thought that the boys were odd, their parents assumed that it was normal for identical brothers to behave in exactly the same way. Then their mother started to become increasingly apprehensive about her sons' ability to perceive weird things no one else could see, to the point where Tricardy, Dicardy and Boo noticed the strain growing between their parents. It didn’t worry them; they just carried on piling up planks, corrugated sheeting and wooden crates until they had created a rickety structure large enough to accommodate all three of them, Del, the family dog, and any alien who might have dropped in. It was quite dangerous so, one night, their father dismantled the structure before it collapsed.
Tricardy, Dicardy and Boo expressed no annoyance at this act of vandalism, which the adults found more disconcerting than a triple tantrum. 
During the ensuing argument between their parents, they overheard their mother tell their father that she had brief relationship with a young man at a motorway hotel over nine years previously. This confirmed their father’s suspicion that the strange triplets were not his, though the boys couldn't understand why it made him so angry. 
With a supreme effort, he overcame his outrage, and spent the following evenings in the local pub sulking or flirting with the barmaid. 
In a few weeks life returned to normal; the boys building another dangerous structure and their mother behaving as though nothing was wrong.
Then Tricardy, Dicardy and Boo saw a young man arrive at the house. He hesitated at the front gate as though expecting Del, the elderly family spaniel with few remaining teeth, to attack him.
Even from the bay window, the triplets could see that the visitor’s eyelashes were unusually long and dark, like theirs, and his skin had that yellowish pallor, which doctors had once thought was jaundice. He had not come in a taxi or car, and it was several miles from the nearest railway station. Perhaps he had landed in his spaceship?
The boys somehow knew the stranger had come to see them. They dashed out to meet him before he could reach the front door.
“Father is at work...” said Tricardy.
“And mother is ironing,” said Dicardy.
“And they didn’t speak to each other this morning,” giggled Boo.
At the last comment the young man’s eyes opened wide.
“Did you want to see her?” asked Tricardy.
“I can fetch her,” offered Dicardy.
“But we don’t really want to,” giggled Boo.
“She’s in a very bad mood.”
“Why not talk to us instead?”
“Not many people talk to us.”
“They say it’s too confusing.”
As the triplet’s responses merged, it was easy to see why.
“I have come to see you,” announced the young man.
“Why?”
“We don’t know who you are.”
“I know who you are,” the visitor told them.
“Who are we, then?”
“The same boy.”
“How can we be the same boy?”
“It’s complicated.”
“That’s what mother says.”
“All the time.”
“Are you sure you don’t want to see her?”
The young man noticed a neighbour glowering suspiciously at him.
“Say nothing to her. I must go now. Meet me here at midnight without waking your parents.”
And he strode away.
The triplets looked at each other. They didn't speak because they were all thinking the same thing.
Leaving the house at the dead of night was not easy. Slipping the bolts on the back door without waking Del was the most difficult part. If he woke up he would demand to go for a walk and howl if they refused to take him.
Del woke up. 
Tricardy quickly fastened his lead and took the elderly spaniel with them.
The boys would never have done something this risky if the young man had not been so familiar. They instinctively knew that he would tell them something their parents had been keeping from them. The stranger was waiting for the brothers on the other side of the front gate. He beckoned to the brothers, so they followed. Even if Del was virtually toothless, it was so dark he might have been ferocious for all the young man knew.
Tricardy, Dicardy, and Boo, in their dressing gowns, and Del, anticipating a romp on the heath, reached the hollow where children lit bonfires and roasted potatoes. Even in the moonlight the place seemed familiar until the spaniel, which had been running ahead of them, suddenly stopped at the sight of a dome pulsing with a dull glow. It was higher than the garden shed, but concealed from the nearby houses by a stand of trees. As the triplets approached, the pulsing of the light increased as though it recognised them.
Tricardy was tempted to reach out and touch its surface. “Are you an alien?” 
Dicardy joined him. “And experiment on humans?” 
“We wouldn’t like that,” giggled Boo, placing his hand on the dome. “It feels really funny - like lots of ants crawling on my skin.”
“It will do you no harm,” the young man reassured them.
“That’s what adults say when they know it will...”
“But we never listen to them...”
“But we trust you. You have long eyelashes, like ours.”
"And are yellow."
The young man at last explained. “About nine years ago something dreadful - and quite wonderful - happened. It was because of me you came into being.”
“We know how that’s done.”
“Mostly.”
“Adults do very silly things,” Boo giggled.
“When I met your mother I had never encountered a human so attractive before. She did not realise who I really was. I should have known better than to make love to her and been aware of what could happen. The genetic compatibility to create a child is only temporary and very limited.”
The triplets, not understanding a word, were now convinced he came from another planet.
“Who are you?” asked Tricardy.
“You have to tell us before we listen to you.”
“Even if that is very silly as well.”
The young man stood against the dome, silhouetted by its glow. “We are your father. I am Jepat, Colos and Varin.”
As the young man spoke his silhouette divided into three parts.
“My name is Jepat,” said one.
“Mine is Colos,” said another.
“And I am Varin,” explained the last. “Together we are one.”
The triplets were too astonished to say anything.
“On this world you should also be one. The trinity of being can only exist on my planet.” 
Each manifestation of their true father reached out to the equivalent of his corresponding son. Tricardy, Dicardy and Boo took the offered hands and grasped them. As they did so the triplets' bodies merged and became one sturdy young boy. 
Jepat, Colos and Varin reverted to the good-looking young man who had helped them make sense of their existence.
The children who had been christened George, Alan and Robert never saw him again. He may have solved the conundrum of who they actually were, but not how their mother was going to explain the triplet’s disappearance to family, friends and neighbours and arrival of a new son. 
At least her husband was more inclined to accept the tall, handsome child as his, unlike the tiny, irksome trio forever finishing each others sentences and building contraptions to welcome aliens.