Mumbai, Oct 8 (IANS): Filmmaker-choreographer Farah Khan Kunder has penned an emotional note for Shah Rukh Khan's wife Gauri Khan where she said that the strength of a mother is second to none.

Gauri Khan turned 51 on Thursday and the Bollywood's power couple is facing a tough time after their son Aryan Khan was arrested by the Narcotics Control Bureau (NCB) in a drugs related case.

Farah took to her Instagram and penned a heart-warming wish with a throwback picture featuring Shah Rukh and Gauri, whom she called "the strongest mother".

Farah wrote: "The strength of a mother is second to none! The prayers of a parent can move mountains & part seas.. HAPPY BIRTHDAY to the strongest mother and woman iv personally witnessed this past week.. @gaurikhan here s wishing you the best birthday present today ??????. #throwbacklastmonth pic credit: @farahkhankunder."

Gauri's daughter Suhana Khan has also wished her mother with a black and white throwback picture of her parents.

In the image, Gauri and Shah Rukh are seen lovingly holding each other as they pose for the lens.

Suhana captioned the picture: "Happy Birthday Ma", followed by a heart emoticon.

Aryan, 23, was arrested by the Narcotics Control Bureau (NCB) along with seven others on charges of consumption, sale, and purchase of narcotic drugs, after a rave party was busted aboard a luxury cruise liner.