Leonardo DiCaprio and Robin Thicke attend memorial for Growing Pains star Alan Thicke

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Leonardo DiCaprio joined mourners at a memorial service honouring his former Growing Pains co-star Alan Thicke.

Alan, the father of singer Robin Thicke, died from a heart attack last week aged 69.

He played Dr Jason Seaver on the US comedy series, which aired from 1985 until 1992.

Alan Thicke with wife Tanya in 2013
Alan Thicke with wife Tanya in 2013 (Richard Shotwell/AP)

Leonardo, who appeared on the final series of Growing Pains, joined Robin and Alan's two other sons for the service at the late star's ranch in California, Entertainment Tonight reported.

About 150 people attended the memorial on Sunday, including Alan's widow Tanya, Kris Jenner, Kevin Costner and songwriter David Foster, ET said.

Robin posted a heartfelt message on Instagram following his father's death.

The Blurred Lines singer wrote: "He was the best man I ever knew. The best friend I ever had.

"Let's all rejoice and celebrate the joy he brought to every room he was in."

He later posted a photo of Alan, with the caption: "Miss you pops. The best."