Jonah Hill. Photo by Andy Kropa/Invision/AP

Jonah Hill still finds his brother's death "painful" to talk about.

The 'Wolf of Wall Street' actor's older sibling Jordan Feldstein passed away from a pulmonary thromboembolism - a blood clot in the lungs - aged 40 last December and the 34-year-old star is still devastated by the loss.

Asked about his brother during an interview with DJ Howard Stern, Jonah declined to talk about him and explained: "The only reason I don't want to talk about it, is because it's painful... Not out of disrespect. But I miss him and I love him and I wish he was here."

The 'Mid 90s' director doesn't go out partying much himself because he doesn't drink as he hates how he feels when he's hungover.

He admitted: "I don't drink. I just don't drink. I just don't party. I like to be healthier. I like to be in a good mood.

"Being hungover affects your mood -- to me at least. I support people who are living their lives and being happy."

But Jonah does have one "f***ed up" vice he's desperate to quit - smoking.

He said: "I'm a human being, so I'm trying to quit smoking. That's a really f**ked up one. It's the last thing I'm working on."

The 'Maniac' star is very close to his younger sister, Beanie Feldstein, and insisted the 'Lady Bird' actress hasn't followed in his footsteps because her passion for acting started long before his.

He said: "My sister's 10 years younger than me. She's my best friend in the entire world. I wouldn't have made it through life without her.

"She wanted to be an actor way before I did. She's been acting since she was like three. I fell into an accidental, very exciting, 15-year acting career."