Apple CEO Tim Cook is joining the board of directors of Robert F. Kennedy Human Rights, a nonprofit organization founded by the Kennedy family. Cook has been an outspoken CEO, personally defending equality and civil rights.

In December 2015, Cook already received the Ripple of Hope Award from the nonprofit organization. But Apple’s CEO is taking its public involvement for human rights one step further with today’s announcement.

“Tim knows the importance of advocating for and representing people who have not been heard,” Robert F. Kennedy Human Rights president and CEO Kerry Kennedy wrote. “He has integrity and does not shy away from challenging issues when he knows they are right and just. Tim is deeply committed to the social justice work that he is helping Robert F. Kennedy Human Rights accomplish.”

According to the organization, Robert F. Kennedy had been a role model when Cook was growing up in Alabama. Robert F. Kennedy Human Rights delivers the RFK Human Rights Award and supports human rights advocates.

Cook has been very private about his personal life and beliefs. But this changed when he publicly revealed he was gay in October 2014. He used this opportunity to pen a Businessweek essay saying he was “proud to be gay.” Here’s what he wrote at the time:

I don’t consider myself an activist, but I realize how much I’ve benefited from the sacrifice of others. So if hearing that the CEO of Apple is gay can help someone struggling to come to terms with who he or she is, or bring comfort to anyone who feels alone, or inspire people to insist on their equality, then it’s worth the trade-off with my own privacy.

Last year, Cook also wrote an op-ed in the Washington Post to call out pro-discrimination laws hiding behind “religious freedom.” In particular, he feared a law in Indiana would lead to discrimination against people in the LGBT community. Lawmakers later voted an amendment to protect the LGBT community.