Krystal expressed much love for her sister Jessica on her birthday. 

Jessica is turning 30 on April 18. In celebration of the special day, Krystal dedicated posts for her sister on her Instagram story. 

Along with cute selfie videos with the captions, "Happy bday" and "I luv u," Krystal also shared a childhood photo where she and Jessica are looking mighty adorable in red outfits. 

Aren't they the cutest?