Complex sentence: Tossgirl was first introduced to Starcraft by her father in 1999, and she and her sister Seo Ji Seung "ZergGirl" both started to play avidly.
Split into simpler sentences: Tossgirl was first introduced to Starcraft by her father in 1999. ToSsGirl and her sister Seo Ji Seung "ZergGirl" both started to play avidly.