The 'Keeping Up With The Kardashians' star is desperate to do anything he can to help his brother-in-law, after he was found unconscious following a drug and drink-fuelled binge.
A source told the Mail Online: ''Rob is willing to do whatever it takes to help Lamar recover. If that means donating a kidney then so be it, Rob has a big heart and he's willing to step up to help his friend.''
The 28-year-old sock designer will still need to undergo tests to find out whether he is a match for Lamar, who is undergoing dialysis, which removes excess waste and water from the blood.
Meanwhile, a source previously revealed Lamar - who is married to Khloe Kardashian - is taking two steps forward and one step back.
They said: ''It's two steps forward, then a step back, but it
does feel like some progress is being made, little by little. There's still a black cloud, like, 'Okay, what's next?' The pneumonia was a huge setback, and now there's worry about permanent scarring of the lungs. His kidneys are still not functioning correctly, but he's nowhere near strong enough to even think of a transplant, so he's on dialysis.''