1.i have 1 older sister,1 older brother and 1 younger sister.
You use different words for your siblings based on your own sex.
A. for male: 난 누나와 형, (그리고) 남동생이 (하나씩) 있어. (하나씩 = one each)
B. for female: 난 언니 하나, 오빠 하나, (그리고) 남동생이 하나 있어. (emphasizing "one")
* for male: 형(older brother) and 누나(older sister).
* for female: 오빠(older brother) and 언니(older sister).
* common to male and female: 남동생(younger brother), 여동생(younger sister), 동생(younger brother or sister).
* other general terms:
-- 형제(brothers, or sometimes "brothers and sisters").
-- 자매(sisters).
-- 남매(brothers and sisters = siblings involving both sexes).
2. i have 3 siblings.
- 나는 형제가 셋 있어 or 난 형제가 셋이야. * 형제 in its broad sense of "brothers and sisters".
(Other ways of saying the same thing)
- 우리는 4(사) 형제야 (We are siblings/brothers of four). This means either "4 brother and sisters", or "4 brothers".
- 우리는 4(네) 자매야 (We are sisters of four).
- 우리는 4(사) 남매야 (We are mixed sex siblings of four).
3. My family members are 6 peoples including me.
- 우리 가족은 [식구는] 나까지 여섯 명이야. * 가족 = family, or a family member, 식구 = a family member.
- 우리 가족은 나까지 합쳐서 여섯 명이야.