생기다 is something coming into existence, and what precedes it usually names the cause or purpose: 화산 폭발로 인해 생긴 칼데라 'a caldera formed by the eruption', 덜 다치기 위해 생긴 굳은살 'calluses that formed to keep you from getting hurt', 명의와 사용자가 달라 생기는 문제 'problems that arise when the name and the user differ'. Note that 생기다 also means 'to look like', which is the sense in 생긴 것만 비슷해, 'they only look alike'.