Beyonce's sister Solange Knowles is married to 56-year-old director Alan Ferguson. But yesterday Solange fans were taken aback, after a video was leaked on Instagram, showing Solange grinding on a mystery man.

In the video, Solange is intimately dancing with the handsome man - who is much younger than her husband.

As you can see in the below video, the man has his arms wrapped around Beyonce's sister's waist - and he is grinding his pelvis into her butt as the two dance slowly.

Solange is seen moving seductively from side to side, in synchronization with her good looking partner.

It's not clear what the relationship is between Solange and the man in the video.

Here is the video:

Here is a screenshot:

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Solange Knowles is a singer, songwriter, record producer, and actress. She started her career as a backup dancer for Destiny's Child, which featured among the members her sister, Beyonce. At age 16, she signing with her father Mathew Knowles's Music World Entertainment label and released her first studio album Solo Star (2002).