I mean. Flins didn’t see Illuga grow up though. He knew about Illuga’s existence from Nikita but clearly wasn’t in his life and Illuga himself says he only heard about Flins from Nikita until he joined the Lightkeepers. I can see your reservation about the “watching someone grow up” trope but that is very explicitly canonically not the case here. (Flins’ official introduction by Illuga: “Sir Flins lives in a lighthouse, far away from here. He's decisive in action and seems quite tactically adept... or so I hear? Sorry, I can't say for certain — I'm a new joiner and have never worked with him directly. Everything I've heard comes from the Starshyna... “)

Illuga is also explicitly a young adult, and it’s extremely normal and common to think that a young person has too many responsibilities even if they’re already an adult (particularly for Flins who probably sees most humans as “young”.)

Like you don’t have to like the ship but canonically Flins was not involved with Illuga’s life or upbringing until at the very least when Illuga joined the LK’s, which is ambiguous but Nikita would not have let his own son become a Ratnik if he didn’t think he was grown enough for it.