It's been a summer of grief for Sylvester Stallone. His son, Sage Stallone, died six weeks ago and now his half-sister, Toni Ann Filiti, lost her battle with lung cancer.

Filiti, 48, died Sunday at the Santa Monica, Calif., home of her and Sly's 90-year-old mother, Jackie Stallone, the New York Daily News reported Monday. Sylvester Stallone's half-sister had been in a California hospital but returned home for her last days when her lung cancer traveled to her brain.

"I was holding her in my arms. I had just washed [her] face and told her how pretty she looked, and she just fell asleep," Jackie Stallone told the paper.  "She's too young to go, but she wasn't feeling any pain. What a terrible month. First Sage and now Toni. It's hard. At least they're together now in heaven."

Filiti and Stallone shared a mother, although Sly's father is Frank Stallone and Filiti's is the daughter of Anthony Filiti, according to UPI. Jackie Stallone is now married to doctor Stephen Marcus Lavine; the couple wed back in 1998.

Sylvester Stallone's son, Stage Stallone, 36, was confirmed dead July 13. The cause of death is pending toxicology results.

Sage's death hit his father, 66, hard.

"It's tough, it's very very tough," Stallone told "Good Morning America" as reported by TMZ. "But if you have good friends and your family's support, it's just something that's a horrible situation but ... hopefully it will heal and you try to get through it but it's something that is a reality in life."

The deaths of his half-sister and son come at a time when Sylvester Stallone is promoting his new action film, "The Expendables 2." The film was tops at the box office over the weekend and has grossed more than $52 million so far, according to Box Office Mojo.