The 70-year-old rocker was criticised last week when pictures emerged of him canoodling with 27-year-old ballet dancer Melanie Hamrick just months after his girlfriend's suicide, but Randy Bambrough - L'Wren's sibling - insists there is no bad blood over Mick's decision to move on with his life.
He told the Daily Mirror newspaper: ''I continue to have a very warm relationship with Mick and have never questioned his love for L'Wren and how important she was in his life.''
Randy also dismissed claims his sister's suicide had anything to do with Mick and Melanie, who reportedly met just a few weeks before L'Wren's death in March.
Sources have suggested they only began dating very recently.
Randy said: ''Usually I ignore these stories, but to suggest that my sister committed suicide because of a false accusation that Mick was involved with another woman is completely ridiculous.''
Randy's support of Mick comes after L'Wren's estranged sister Jan Shane blasted the Rolling Stones frontman for moving on so quickly and thinks he ''contributed'' to her untimely suicide.
She said: ''I do believe that he contributed to it more than he realises or will admit...
''My sister deserved so much more than that. It's a terrible thing for Mick to have done. It's sad.
''His life goes on as if nothing happened. He's still out with women, but a huge part of our family is missing.''