Meredith Burke
Meredith Scanlon (née Burke) is the eldest daughter of Monica Burke and Russell Burke and older sister to Mel Burke. She was charged and found guilty of co-conspiring with her husband, Lewis Scanlon, in running a large scale, multi-million-dollar fraudulent investment operation. Her criminal involvement and subsequent incarceration resulted in a huge scandal for the political Burke family, with Mel being awarded full custody of her two adolescent children, Lennox and Ryder.
Meredith came to Melissa's house for Christmas, having been allowed to leave jail only for that occasion. Little is known about her personality, but she and Joey aren't what you would call 'old friends'. It is implied that Meredith was just as wild and rebellious as Mel in her youth, and that like Mel, she did not have a good relationship with either of her parents.
Given that Lennox and Ryder are now approaching their mid-teens and Mel is in her early thirties, it can be concluded that Meredith is either significantly older than Mel or got married and had children at a young age. Her current marital status with Lewis is divorced (we're told this in Season 3 Episode 16)
It is also unknown how long of a sentence she is expected to serve or where she is incarcerated. Neither of her children or Mel seem keen on visiting her in prison.