Peter Rive, the co-founder and CTO of solar panel company SolarCity, will leave Tesla to focus on other projects and spend more time with his family, according to the company. His departure comes just eight months after SolarCity was purchased by Tesla for $2.6 billion in stock and two months after Tesla opened up pre-orders for the Solar Roof, which puts solar panel components in glass tiles for a more camouflaged look.

Rive was at SolarCity for 11 years prior to the company’s sale to Tesla, and it eventually became the largest solar panel maker in the US. Prior to SolarCity’s sale, it was in the process of building a solar panel “gigafactory” in Buffalo, New York, much like Tesla’s electric vehicle and battery Gigafactory in Nevada

Lyndon Rive, Peter’s brother and the other co-founder of SolarCity, also left Tesla in May, reportedly to explore other opportunities in entrepreneurship. Tesla CEO Elon Musk is the cousin of both Rives.

SolarCity’s sale to Tesla was initially a contentious one, with some investors concerned about Tesla taking on SolarCity’s debt (although Musk tweeted that he’d repay the company’s debt personally, if need be). But the Rives and Musk went to work convincing shareholders that the move was the right one. Tesla teased a partnership with solar panel maker Panasonic at the Buffalo factory if investors approved the sale. (Panasonic also partners with Tesla on battery construction at the Gigafactory.)

The company also announced the Solar Roof, telling investors that there was no way for the sleek tiles to be made without Tesla owning SolarCity. The bid worked, and investors overwhelmingly approved the purchase. After the sale, Tesla started phasing out door-to-door sales in favor of exposing customers to the brand at Tesla-owned retail outlets. The thought seemed to be to pass on selling volume and go for the most profitable projects, including solar roof tiles.

By May, Tesla opened up solar roof pre-orders for customers who put $1,000 down. Solar Roof tile production is supposed to start this summer.

In a letter published on GreenTech Media, Peter wrote, “Tesla is the most important company on the planet when it comes to accelerating our transition to sustainable energy, which has made my decision very difficult—there is no other company that can be more impactful in our fight against climate change.”