Did You know that...
Here was a good story from Wikipedia:
In 2002, Krystal began appearing in television commercials. She first appeared in a Lotte commercial with Korean actress Han Ga-in. In 2006, her parents allowed her to join SM Entertainment, and the agency enrolled her in dance classes, including hip hop and jazz.
What to say... I wonder if Krystal would debut with Jessica in SNSD if her parents would let her be a trainee in a early age. But I personally don't think she would do that. The age differece between the two sister is 6 years and the difference between the oldest and the youngest one in SNSD is 3 years. <-- My calculation XD
Truth to be told, they aren't that alike but the positive thing is that they'll have each other in the same agency ^^ However i wouldn't be able to be in the same company as my little sister =__= Oh dear lord NEVAH! Yeah our relationship isn't that good Dx