Disclaimer: Harry Potter belongs to JK Rowling, not me.
It is traditional for Pureblood families to only announce the births (or rather existence) of their children when they exhibit some sign of accidental magic. In the old times, before the trials and Statute of Secrecy it was even common not to name a child until it had reached this point. It's easy to guess what happened to the children who never showed magic but it's less bloody than one might think. Depending on your perspective, that is. A child would be laid outside the wards of their family home and left to fend for themselves, some survived and went feral, some were found by muggle but of course the majority perished. But, while the Malfoy and Black families were proud of being the most traditional of modern Wizarding lines they only adhered to the first of the traditions, and as times had changed the birth was recorded by the Ministry (presumably so they wouldn't be tempted to stick closer to tradition if the child didn't exhibit signs of magic). So, while his birth and death were recorded by the Ministry, nobody but close family ever heard of Scorpius Malfoy.
Draco still went into bathrooms to think.
It was two weeks before Draco's sixth birthday, he remembers this because that morning his mother had started her tradition of giving him a small gift on each day leading up to his birthday. His first present had been a packet of the new animating crayons (ones that actually made the pictures move properly, not just walk around the page waving) and Draco was in the middle of a large drawing of a group of dragons that kept running away from him giggling when he tried to shade in their wings. His father had told him that the Hogwarts motto was 'Draco Dormiens Nunquam Titillandus' when they visited real dragons the previous month and he was beginning to realise that it was very hard not to tickle a dragon, even colouring their snouts sent them into giggles.
The baby is upstairs and Draco is glad because now he can crawl he has started grabbing Draco's things and putting them into his mouth. He has a special habit of doing that just after he's eaten so it leaves everything coated in food as well as dribble. And the baby is taking away all of mummy's time now, even though the elves could look after him and leave mummy for Draco who is actually fun and can speak and play, not just grab and dribble. But mummy wants the baby to do magic like everyone else can so she stays close to him. Draco has been able to do magic forever and can make colours and lights when he tries really hard. But his mummy just wants to watch the baby and sing songs to it even though the baby can't even sing along like Draco can. And the baby doesn't know about scales and Draco does and Draco sang a song on mummy's birthday and everyone clapped and mummy smiled and smiled and said that it was the best present ever.
But mummy needs to spend time with the baby now. Draco pokes out his tongue in concentration and manages to catch one of the dragons with the purple crayon, he quickly colours one wing before it squirms away. They're silly, because they don't know that he could just rub out their wings and then they wouldn't be able to fly away. But it's fun chasing them. He smells something sweet and focuses, trying to see if its cakes for dinner but it's too flowery so the baby must be having a bath. Draco turns back to his drawing; he did not want to go upstairs at bath time. Last time he had done that the baby splashed everywhere and got bubbles into Draco's eyes and then they went all red and father told him off for crying even though he hadn't.
Dobby is Draco's favourite elf and he wonders if he could sneak out of the play room and into the kitchen to ask him for some coconut ice to eat. Mummy didn't like him eating sweets in the afternoon so he had to be careful to sneak it, though he always ended up telling her about it afterwards. Once he had heard his mother joke to his father that she didn't know where Draco's conscience had come from, and his father got worried about Draco maybe not being a Slytherin. It was confusing, how sometimes his father wanted him to be naughty and sometimes he told him off for it. It was easier just to be good and have his mummy call him her good boy and her angel, because she was too scary when she got angry.
He was still thinking on this when he decided he really did want some coconut ice and stood up on tiptoe ready to sneak, but when he touched the doorknob he heard a scream. It took him a moment to realise that it was a lady's scream and that lady was his mother. His mother was hurt and it was his duty as the only gentleman present to defend her, to save her. His father would be so proud that he might even give him one of the rare hugs that were saved for Draco's birthday. So he ran up the stairs into the bathroom, his mother screaming the whole time. The elves were popping up around him and tried to keep him away from the bathroom door but he pushed them away and he opened it.
He opened it and there was water all over the floor and all over mummy and she was holding the baby but there was something wrong and she looked at him and started crying and the baby was blue and surely babies shouldn't be that still and she stared at him and cried and the elves tried to move him away but he wouldn't go and he tried to take the baby and his mother hit him and it was hard and he fell against the side of the bath and his shoulder started bleeding and they sat there and she cried and his father came and picked him up and the elves put him to bed but all he saw was blue babies and he could hear mummy crying and his shoulder hurt from falling and he knew something was wrong but no-one would tell him what.
She spoke to him about it only once, years later when Astoria was pregnant. She had left the baby in the bath for a moment whilst she went into her bedroom to fetch a new bottle of shampoo. He hadn't even cried as he sunk under the water. The stuffed unicorn that was kept in his cot was next to him in the bath, soaked through. He was exhausted after his first display of accidental magic and he lost his sitting balance and fell backwards.
Draco never let himself be submerged in water after that, when the other children learnt how to swim he smirked and said that there were spells to stop drowning so only muggles needed to learn. He had nightmares for a month after the second Triwizard task. He couldn't be in the room when Astoria bathed their child, but he sat a vigil outside the bathroom door in case of an emergency.
In Draco's sixth year he spent a lot of time in bathrooms, talking to a ghost. He would sit on the tiles and think about babies and water and not being able to save his mother. And then Potter hit him with that curse and he thought about water around him and blood and blue. The ghost wanted to talk about death and he did too but she didn't have the right answers so they just talked about being sad, and being scared, and not being able to help people.
Only Draco and his parents remember the first Scorpius Malfoy, and each of them wonder if they could have changed things, if Draco hadn't been selfish and had wanted to help his mother with the baby, if his father had realised that his family was more important than their seat on the Wizengamot, and if his mother had got the shampoo before putting the baby into the bath.
Author's note: The idea of Purebloods culling their squibs was something I picked up via the wonderful Vera Rozalsky's 'Paterfamilias', which you can find on this site.
So, a little depressing one-shot. Drowning babies (that is, babies that drown) is something that really sticks in my mind as something full of horror, both from Bright Eyes' song 'Padriac My Prince' and one of my mum's stories from her nursing days wherein a mother was bathing her baby when she heard an older child scream as it fell into the fireplace of the next room. Naturally she runs and saves the older child and returns to the bathroom to find that the baby drowned in her absence. Awful, huh?