Their younger brother, Carlo Mendez, confirmed the news on his Instagram page, writing that Carlos "fought with all his might and power," and said he leaves behind two children, ages 13 and 5.
He also took to Instagram to write about his late brother's memorial service on Tuesday: "To remember who my brother was and the impact he left on us. The amazing person he was, the funny charming genius comedian creative hot tempered crazy calm person that he was."
With absolute pain and sadness in my heart this is the hardest thing I've ever had to go through in my life and as I'm writing this I'm still in disbelief. My brother has passed away peacefully this morning. I want to thank you all from the bottom of my heart for those who have prayed and have kept my brother in your thoughts and who wished him to get better. He fought with all his might and power and gave cancer one hell of a fight. He leaves behind behind a 13 year old and a 5 year old. I love you my brother may god bless you and I'll see you once again.
Three weeks ago, the Lost River actress, 42, shared a black-and-white photo of herself with her older brother at the Hollywood Stands Up to Cancer event in January 2015, captioning the image with a heart emoji.
Mendes introduced Katie Couric at the event, and told the audience that "tonight I'm here with my family and my brother Carlos, who had [cancer] treatment today."