Melissa Hecox is the older sister of Ian Hecox in Real Life. She was first mentioned in Ian is Bored where Ian was checking his fake family tree and mentioned that he has a sister. Many think she is deceased or believe another equally morbid circumstance. However, all rumors are false.
She was also mentioned in a Lunchtime w/ Smosh as Ian mentions that she is his older sister and she is a fan of Britney Spears and has a fondness for art. She is either abroad or married in a different city, but as far as viewers know she isn't living close to Smosh.
She is also mentioned in their Mothers Day song when Ian says he put the plastic from a Snapple cap in her drink and she choked on it.