The character talks how everything he wanted etc ever since long ago he just copied his brother. Even going to uni he did because his parents told him. this lead to him feeling undecided and not developing an ego
Then he add:
"兄貴を見ながら安全ライン" I understand the sentence is akin to "Even when it comes to what to do, while I looked at my brother..."
however I'm struggling to understand this use of 安全ライン here. Especially given ながら use but there is no other verb
安全ライン refers to marks on the ground/floor to indicate safe areas (like on train platforms, roads, factories).
何やるのも安全ライン
This sentence is arguably more correct to write 何やるにも安全ライン, and the mental image is that you draw on the concept 安全ライン whatever the topic is. 兄貴を見ながら adds the fact that the 安全ライン is defined by what the older brother does.
So the person is carefully watching what their older brother does, and only ventures within the "front" the older brother established.
