The 'Jung sisters' - SNSD's Jessica and f(x)'s Krystal - are both celebrating happy days lately, thanks to their individual events and achievements. On April 18th, Jessica will be celebrating her 23rd birthday. After debuting with SNSD back in 2007 when she was just 19 years old, Jessica is said to be more than happy with the success her group has achieved over the past four years, and is taking part in a small birthday gathering with her closest friends. Jessica's younger sister, Krystal, is also looking towards a successful promotion cycle with f(x)'s "Pinocchio" impending comeback this week. On the same day, the title track for f(x)'s first official album, "Pinocchio", was released online for the first time. Currently, the song is dominating live charts on major music portals like Melon, dosirak, Cyworld, Bugs, and Soribada. The achievement is quite formidable, considering that the group debuted only a year and seven months ago. Happy birthday to Jessica, and congratulations to f(x)! Source: Star News via Nate