Taehyun is the perfect person to advise his own brother. Everyone think that being an idol

is a fairytale. Nam Taehyun knows that is not the truth. He is being there for his little brother

so he knows to focus and come to him if he is confused, pressured or mistreated about the crap

they try to pull on gullible preteens.

The best person to give advice is someone that has been 'in the middle'. In other words they didn't fail as an idol but they still left. That gives them a more balanced outlook. Tae Hyun left because the pressure was too much and it affected his mental health. He's had dinner with the Winner members since then and has made it clear it was never about bad blood. He just didn't fit as an idol. He can advise his brother of how difficult it is and how much hard work without telling him he's going to fail or that no one should be an idol. With other people they would just tell them aim for a high rank and work hard and you'll succeed or if they had a bad experience they would caution not to get their hopes up. Instead Tae Hyun is giving realistic advice. He's telling him to work hard and learn and from there he'll know if this is right for him and if he can succeed.