Hey Y'all! Thanks for checking out this story - It's my first one. Let me know what you think of it!

(Obviously I don't own Harry Potter or any of the characters except my OC)

Full Summary:

Neville managed to brew one potion right. And much to Severus Snape's horror, it uncovered a truth that connected him to his most hated enemy – Sirius Black. What's a poor spy to do when his newly found sister also has an escaped convict for a brother? Elspeth Moore always knew she was adopted, never sparing her biological family more than the odd thought. But that all changes when she gets a letter from someone who claims to be her brother.

Chapter 1: A Premature Corpse

He should have risked death by pastry, it would have been much preferable to this. Sure, it may have been an uncomfortable death, but bloody hell Neville was so familiar with being uncomfortable at this point that it would have been a fitting end. All he would have had to do was test the twins' stupid untested joke pastry and his stupid luck would have ensured his very fitting death so he wouldn't have had to live to be in this stupid, awful, bloody classroom with bloody Professor Snape sneering over him covered in Neville's bloody, stupid potion. It would have been the better death.

But no, Neville needed to be in potions – he needed to. He had to be an auror just like his dad – he had to make his grandmother and his parents proud. Aurors needed potions class so Neville needed potions class. And with that bolstering thought in mind, he had turned down the twins' offer of testing one of their joke products that would get him out of class. But his brave attempt to actually try to get something right backfired so spectacularly that he was now a dead man.

Here he was, a premature corpse, with his perfect potion (the first potion he has ever gotten even close to correct!) covering his greatest fear (the boggart even confirmed it) that was standing right in front of him most likely contemplating the gruesome details of his no doubt very painful and drawn-out death.

When Professor Snape told them last week that they were going to be brewing the basic heritage potion today, Neville knew that he had to brew this one right – he just had to. He had to see his family tree with his name right underneath his parents', proving once and for all that he was, without a doubt, their son. So, he did what any self-respecting Gryffindor would do when they needed to do well; He asked Hermione.

All weekend he stayed with her in the library discussing in agonizing detail how to brew this stupid, bloody, needed potion. Every ingredient was analyzed. Every stir of the stir stick was paced to perfection. Absolutely nothing was overlooked. Well…his other homework was left alone but he had to get this potion right, nothing else mattered if he could just prove that he was the child of Frank and Alice Longbottom.

But it was as if Fate needed to remind Neville that he was, in fact, Neville Longbottom because Neville Longbottom cannot brew a potion without something going wrong. It always did. And it always happened to him.

Severus Snape considered himself a patient man. Oh, he knew many people did not think he had even the smallest amount of patience but by Merlin were they wrong. He had to teach multiple classes for each of the seven years of potion classes at Hogwarts. He had to deal with a throng of issues ranging from little idiots not being able to cut with a knife to the bigger, only slightly less idiotic idiots who incorrectly mix volatile ingredients together. He should be given an Order of Merlin just for keeping the dunderheads alive at this point. Severus was sure that somehow each new generation was dumber than the last.

His worst offender by far stood in front of him. The child managed to blow up a heritage potion – a heritage potion. There is nothing even remotely explosive in a heritage potion. It's a heritage potion. How in the name of Salazar did he manage to blow up a fucking heritage potion?!

"Professor, are you alright?"

Ms. Granger was the first to break the silence that had fallen over the classroom, but his answering scowl was all he gave her.

"Mr. Longbottom. What…did you…do" Severus was proud of the way he managed draw out each part of his question, deepening his scowl with each word. He took great pleasure in being one of the few members of staff who got more terrifying the quieter they became. Poppy often teased him that he was emulating Minerva to which he vehemently disagreed even though she was also one of the few who could pull off these intimidation tactics.

"I-I-I don't know, sir" Longbottom rushed out, "I completed the potion ex-exactly how the book s-s-says a-a-and I-I was ju-just about to bottle it when….well, when it exploded…sir" Severus could see the child shaking through the strands of hair weighed down by the potion.

"Mr. Longbottom. It's evident that you do not know, but this is a heritage potion. A basic heritage potion. Which means that this potion is one of the LEAST volatile potions made in any of the classes. The fact that you made it explode means that you. Did. It. WRONG" Drops of liquid were running down his nose now.

"Please Sir, Neville really did follow all –"

"Not now Granger"

"But it worked –"

"I said not now Ms. Granger!"

He saw Granger grab for the parchment that would have recorded the boy's family tree and shove it his way. "Excuse me sir, but it really did work sir. Neville made the potion right or it wouldn't have recorded your family tree now that it has your hair in it…er…or now that it is on your hair…".

Severus picked up the parchment. Surely Longbottom couldn't have made a successful potion if it blew up. As a general rule, things that blow up don't work, unless they were made to. And this potion was most definitely not meant to explode. But Severus saw his family tree. He saw his father and mother and his grandparents going back several generations. It can't be correct, there must be something that's wrong ah HA! There!

He noticed a small line extending out from his mother, joining with another small label and extending down to another name. This. This right here is the mistake. There is no way this person exists.

"As confident in your abilities as you think you are Ms. Granger, I am pleased to inform you that you are wrong. This family tree is incorrect. I am therefore justified in my taking of 10 points from Gryffindor for Mr. Longbottom's failure to read the instructions, 20 points for endangering his fellow students, another 10 points for failure to see his mistake, and 10 points from you for back talk.

Bottle your potions and bring your vials and parchments to the front. Class is dismissed."

"But sir!"

"That's not fair!"

"50 points?!"

He heard an outpouring of protest but shut the little miscreants down with another glare and spoke up, "If I hear one more word of protest, I will subtract 5 points per person who screams in my class." He heard several of his Slytherins snicker at the abashed lions.

There was no way the Longbottom boy made a potion – made a working potion. This family tree is false. No question about it. Severus' thoughts spiraled into the multitude of ways Longbottom could have ruined the potion, but a niggling of doubt kept whispering "what if?" in the back of his brain.

There was just no way that he could have a sister.

Right?