Before SuperM was born, Taeyong always admired Taemin. In the first episode of their show The Beginning, it showed when they were choosing rooms.
When it was Taemin’s turn to select one, he realized that he was able to get the exact one he’d wanted all because of Taeyong.
Taemin knew Taeyong had selected a different room so he could have the one he’d set his eyes on from the start. He didn’t quite understand why and thought it was because he was older than Taeyong.
It hadn’t been about age at all. Taeyong hadn’t wanted to crush Taemin’s hope for something he’d been wanting. He wouldn’t have been able to rest peacefully if he had.
Taeyong not only admires Taemin but didn’t want to see him upset. See him happily surprise Taemin with his thoughtful choice.