Sirius glared at Remus for bringing up the sister he had once had. She had also been shunned by their parents for being against the Death Eaters and Voldemort. She was exactly like him in every way, she had been his twin sister. Surprisingly enough not many knew about her, she had died in their third year at Hogwarts in the attack that Voldemort had made during his rise to power. She had saved many lives that day, but lost her own in return. In total she had saved nearly 30 lives, including Sirius'. She was soon forgotten at Hogwarts. The only people who really missed her were the marauders and co. mainly being Sirius, James, Remus, Peter, and Lilly. Jamie and Lily had been the closes of friends. Jamie had met Lilly on the train ride of their first year.
Even though Lily, for a long period of time, was against the Marauders, Jamie kept a balance between the two sides. Keeping Lilly from killing each of the marauders and in return keeping each of the marauders from pranking Lily to death and back, and by keeping the love sick James from drooling literally all over Lily, though that did happen, compliments of Snape. Lilly needless to say had been extremely disgusted in him and thoroughly pissed. James got Snape back for doing that to Lilly though.
In short, Jamie was extremely missed by all of the marauders and lily. Sirius the most probably. When they had been kids, their father had a short temper you could say and lashed out at his kids very easily. Jamie, who knows why, would usually get their father to come after her instead of Sirius, who was hit the most for being 'stronger' for being a male rather than a female. Sirius and Jamie were closer to close, they told each other everything, they knew that they could depended each other, and that they would always be there for each other. Even though, that proved wrong in the end.
After the battle on the grounds of Hogwarts, there was a small ceremony for those lost in the battle, 4 teachers, 50 students, and 20 Death Eaters had been killed. Jamie was just another name on the list to the rest of the world and to the majority of Hogwarts also. Sirius and Jaime's parents didn't go to the ceremony. Not that that really bothered Sirius, he wouldn't have gone if they had been there. Pretending that they cared about her, when really they were happy. In fact, when they got the news that she had died, they knew it, they were at the raid themselves.