Taehyung was 18 and Jeongguk 14 when he had the talk.
Jeongguk's parents had decided to give him the talk of love, relationships, intercourses and everything around that. He had almost burnt out due to embarrassment that day, deciding to let Taehyung know that he wouldn't be needing his help with his homework that day since he was too bashed to even face Taehyung. Taehyung, who knew everything about all of this already.
Taehyung had, nonetheless, showed up at his door, asking him if he had been feeling alright since Jeongguk never cancelled their meet-up plans. Jeongguk wasn't even able to look up in his face, standing stiff and timid in a corner, not looking him in the eyes when Taehyung had questioned him about his behaviour to which Jeongguk had awkwardly brushed off saying they should do their homework only for Taehyung to remind him that he had texted him that he didn't get any homework that day.
Jeongguk had frozen in his steps, knowing he was caught as he tightened his hands in fists and closed his eyes, looking down. Taehyung had gotten up and grabbed his fists, opening them and entwining his fingers with Jeongguk's, asking what it was that was bothering him.
Jeongguk had closed the door of his room before telling Taehyung that he knew what people did when they were in love. Oh? Taehyung had said, not quite understanding for a moment before realising.
Oh.
And so he had asked Jeongguk if he liked someone, to which Jeongguk had nodded shyly and admitting there was someone in his class. And even though Taehyung wanted to say no, he had asked Jeongguk more about them, asking him to ask the girl out and see how it goes because, judging from the shy stars in his eyes, it looked like Jeongguk liked her a lot.
And it was at the age of 18 that Taehyung realised how he would sacrifice anything - even his own happiness - for Jeongguk's.