This could turn into a full One Chicago story someday, though right now, I don't really have the time. But because these plot bunnies have been running around in my brain for a while now, I decided to let them out :)

It was hardly surprising that Will met Aaron first. No, that wasn't entirely right. He actually met Lucy first, during that whole debacle with the grenade going off in the ER. But he figured it didn't really count because it wasn't as much meeting her as ending up in a crisis together. Apart from her first name, he had nothing. So it wasn't wrong to say that the first member of the Cohen family he really met - as in getting to know etc - was Aaron.

Since they both worked at Gaffney Chicago Med, it was only a matter of time before the ER attending crossed paths with the ER nurse. However, it was only after a patient had died despite their best efforts that he talked to the younger man about something other than the job.

xxx

Marianne Leigh, aged 16, had been brought in by paramedics after she had collapsed at a party. She was heavily intoxicated and, even worse, on drugs. "We were just having fun", her friend Ava had offered when asked about it, petulantly crossing her arms.

Whatever they had classified as 'fun' sadly became a nightmare for both the patient and the doctors. The mixture of alcohol and what they finally determined to be an overdose of Ecstasy had wreaked havoc on Marianne's system. Her vitals were all over the place, blood pressure and heart rate sky-high. Her body temperature was off the charts and to make matters worse, she was choking on her own vomit because her jaws were clenched firmly shut. Then the seizure hit and it all went south.

After almost thirty minutes of fighting to save the young girl's life, Will was forced to call it. Marianne's body hadn't been able to cope. Renal failure, cardiac arrythmia, O2 sats plummeting. In the end, her heart had given out and after all attempts to resuscitate her had failed, the doctor had been forced to admit defeat.

"Time of death: 01:42", Will announced with a heavy sigh, slowly pulling off his gloves.

The medical team that had crowded the small ER cubicle started filing out, one after the other. In the end, only two people were left. Will and the young nurse with dark blond hair who always wore his watch on the right wrist. What was his name? Adam? Aidan? Aaron. Yes, that was it.

Aaron was still staring at Marianne, sadness etched into his features. Sadness and something more. Something deeper, rawer. Was it fear? Will didn't have time to study the younger man's expression more closely because suddenly Maggie was there, ushering them both out in that decisive but gentle manner of hers.

"Come on", she said, giving the doctor a nudge before moving to the blond.

Aaron startled and blinked at her. "She's so young, Maggie", he spoke, voice quiet before trailing off. Will got the impression that there was something left unsaid, something he couldn't understand.

The charge nurse smiled knowingly at him and patted his shoulder, keeping a hand on his back as she steered him to the door. "Take a break", she advised. "Get some fresh air, grab some coffee." She glanced at Will, signalising him that this was meant for him, too.

Both men just nodded, neither daring (or both simply too tired) to argue.

xxx

"I sometimes wonder how people can do these things."

The admission came so completely out of the blue that it took Will a moment to gather his wits. Aaron was sitting across from him, blue eyes peering at him through a few strands that had fallen into his face. "It's just so stupid. Why would you want to take something that skrews with your mind and messes up your body to the point where it can actually kill you?"

Will shrugged. "I don't know", he offered.

The blond sighed and nodded, gaze dropping to the cup of coffee he held between his hands. "Yeah. Me neither." He shook his head. "Sorry, Dr Halstead, you don't need me ranting at you."

"It's alright", Will replied, waving off the unnecessary apology. "I sometimes go on these rants too." He chuckled and added: "Usually, Jay is the one who has to suffer through them."

A knowing smirk appeared on the nurse's face. "Older Brother?", he guessed.

Will confirmed, a smile making its way onto his features as well.

There was a pause, then Aaron smacked a palm to his forehead. "Of course!", he exclaimed. "Jesus Christ, talk about stupid! Your brother's Jay, the detective!" Seeing the startled expression on the doctor's face, he chuckled, slightly ashamed of his outburst, and explained: "He works with my brother and is pretty close with my sister."

That tidbit of information was what Will needed and it finally clicked. He rolled his eyes at his own blindness and realised: "Lucy. Your sister is Lucy." Suddenly, the nurse's words in the ER made a lot more sense.

Aaron nodded and he continued: "Which means that Oliver is your brother... how the heck did I not see this?"

"Your guess is as good as mine", the blond commented with a half-shrug and a lopsided smile. "I mean, I didn't put two and two together either."

The ice was broken and with the connection of their siblings working together and being friends, conversation began to flow easily between them. Soon enough, Will would gain the friendship of the Cohen siblings, with all that entailed: Sincere smiles, a friendly ear, protective loyalty and unwavering, unconditional support. Not that he knew it yet.
For the moment, they both simply enjoyed the downtime while it lasted. They knew well enough that there would be a new patient coming through the doors of the ER anytime soon.