this video will show you that jihyo is the baby of jyp ent. all of the artist at jyp ent trained with jihyo that's why they were close. And also jihyo trained for 10 years and jihyo was the leader not because she trained for 10 years but the member pick her because she's kind and have all of this  (“Honesty, sincerity, and humility.") motto of jyp ent.