Thirteen- They're in the training room, wrestling. Thin, wispy beams of light filter in through the windows, shining on the two boys on the ground. Will pins Jem down- though he has a sneaking suspicion Jem let him, just so he could have some pride left- and that's when Will has his first jolt that something is wrong with him. Because with Jem grinning up at him, sweaty hair sticking to the mat, Will feels something so incredibly terrible that gets off his friend quickly, and makes excuses not to practice for the remainder of the day.
Fourteen- They stand in the front of the room, facing each other. Will locks his eyes on Jem as his friend's steady hand draws the rune carefully over his heart. Will can feel the heat vibrating off Jem's arm, and it feels so alive that Will tries to force his heartbeat to slow down, because of course Jem can feel it. Judging by the smile Jem shoots him, reassuring and warm, it hasn't worked.
Then it's Will's turn, and he steps up to Mark Jem. And if something in his heart stirs at the look Jem gives him, Will convinces himself it's the new rune.
Fifteen- It's late at night, it's the third anniversary of Ella's death, and for the first time in William Herondale's life he's utterly drunk. He stumbles up the old stairs of the Institute, clumsy in a way that's new for him. Jem steps out of his room, watching his sadly, eyes steady. "Don't." Will slurs. "I'm not a show, James. Not a violin show."
Jem just steps forwards, taking his arm lightly to pull Will into his room. Will goes without a fight- drunk or not, this is still Jem- but as Jem sets him on the bed, Will grabs his parabatai's wrist. "Don't leave."
Jem perches on the edge of the bed. "Believe me; I'm not leaving you like this."
"No. You-you can't go. No- no dying. No."
Jem stares at him, before swallowing. "I'll try."
Will leans forwards, and seals it with a kiss.
They never speak of that night, but unknown to Jem, Will remembers.
Sixteen- Will kneels by Jem, holding the boy steady as he coughs into Will's shirt, forcing himself to be calm. It's hard, in times like these, not to panic, to give into the overwhelming flow of feelings that this cannot be happening Jem cannot die no I won't let him, but he can't. No doubt Jem already has trouble with the idea of dying; Will must not make it harder.
"Mmh sorry," Jem murmurs, voice rough, gesturing to the blood on Will's shirt. Will has a cruel desire to laugh- If you're going to apologize, James, do not do so for an easily replaceable shirt. Apologize for leaving me, completely alone- but of course that isn't Jem's fault.
"It's quite alright," Will says, forcing a light tone. "It was an ugly shirt anyways."
Jem smiles appreciatively, leaning into his friend. "And thank you. It- it makes it easier to deal with it all. Having you here." Jem's voice is quiet with sleepiness, but Will hears him anyway. To deal with it all. Will wonders if maybe that's why they each choose the places for the parabatai rune that they did- Jem's goes on his shoulder, for Will takes some of the weight of Jem's too-heavy shoulders. And Will's on his heart, for isn't Jem the only lifeline he has for his heart? The only thing that keeps it for suffocating itself.
"The same to you," Will replies softly. "The same for you."
Seventeen- Will wonders if maybe he fell in love with Jem's violin first.
The music dances through the cracks between the door and the wall, and Will closes his eyes and lets the melody overwhelm him. It's a cheerful one, and within an instant Will is more peaceful. Of course, it isn't just the tune- upliftling music means Jem's happy, and if Jem's happy, so is Will. So maybe it wasn't the violin.
Will is insanely in love with Jem.
Maybe the violin just helped him realize it, but it is true, and perhaps it always has been. He is in love with Jem's music, his optimism, his courage, his humor, and million other reasons. He may go to hell for it, but that's alright with him- he was heading down there anyways, and he knows it. He will not bring James down with him, though. And if that means hiding his feelings for as long as he lives, pretending to play around with girls- so be it.
And so when four months later, a brunette shows up and Jem gets engaged soon after, Will is in some way glad.
After all, it was never Jem's burden to bare.