Does a bigger gap mean a different generation?

Lines: Hyung/unnie/maknae lines are social nicknames from age order.
Math: Same calendar year ≠ same international age on a given day.
Debuts: A 2015 debut does not tell you 2026 ages — use birthdays.

Not automatically — generation talk is debut-era marketing, not birthday math.

Should I use Korean age?

For Hangul fan talk maybe; for “how old” searches, international age is clearer.

Ages · 그룹 나이 차이 — 형·언니 라인 읽기

Age gaps in K-pop groups