Tesla Chief Executive Elon Musk's brother, Kimbal Musk, who is a Tesla board member, sold 27 million worth of Tesla stock on Thursday, according to regulatory filings. That comes as TSLA stock has retreated in recent days to a critical juncture.

Tesla Inc directors Kimbal Musk and Robyn M Denholm as well as Chief Financial Officer Vaibhav Taneja sold shares of the company over the past week, according to recent filings with the Securities and Exchange Commission.

In many ways, these have been tough days for Tesla. Falling sales. Squeezed profit margins. Proposed changes in US government policy that could cost the company billions.