Carrie Fisher and Sean Ono Lennon were actually good friends. After her passing, he posted several heartfelt photos on Instagram remembering his friend.
Sean has now released a song called "Bird Song" which he had co-wrote with Carrie. On Soundcloud he explained, "Carrie and I used to stay up until dawn chatting and pontificating about life. They were the best moments. Anyway...we wrote a song about staying up too late and hearing the birds sing.
He recorded the song with Willow Smith.