Hugh Hefner's wife Crystal Harris was a ''pillar of strength'' in his final years.

The Playboy magazine founder passed away at the age of 91 last week after suffering a cardiac arrest, and it has now been revealed his 31-year-old spouse Crystal stayed by his side through his ''declining years''.

A source said: ''Crystal surprised the hell out of a lot of people when she stood by Hef's side in his declining years as he got older and became more frail. They actually called Crystal a pillar of strength.''

According to gossip website, Crystal - who married Hugh in 2012 - accompanied her husband to his doctor's appointments, and even set up game and movie nights to keep his spirits up.

The blonde beauty also reportedly stayed by his bed side after he was placed on bed rest, which is believed to have come as a pleasant surprise to his family - including children Christie, 64, David, 62, Marston, 27, and Cooper, 26 - who are said to have been concerned about her motives when she wed the wealthy businessman.

The insider added: ''The family initially was concerned that as Hef got older she wouldn't be there to support him, but she flipped the script with her attentiveness, and we're told the family's immensely grateful for her vigilance.''

Meanwhile, Crystal recently broke her silence following the news of Hugh's tragic death, and admitted she has been struggling to thank everyone for their kind words.

She said: ''I haven't been able to bring myself to write most people back to thank them for their condolences. I am heartbroken. I am still in disbelief.

''He was an American hero. A pioneer. A kind and humble soul who opened up his life and home to the world. I felt how much he loved me. I loved him so much.

''I am so grateful. He gave me life. He gave me direction. He taught me kindness. I will feel eternally grateful to have been by his side, holding his hand, and telling him how much I love him.''