DEREK & JULIANNE GO TOE-TO-TOE TO MEND FENCES!

No storming off in a Hough after sibs kiss & make up

THE long-simmering sibling rivalry between Derek and Julianne Hough has finally cooled -but it took a family crisis to do it!

In a frank interview, 36-year-old Dancing with the Stars co-host Julianne says the duo became close once again after Derek's dancer wife, Hayley Erbert, fell ill following a performance with her husband in Washington, D.C. last December.

Hayley, 29, was found to have suffered a cranial hematoma, with blood pooling inside her skull and causing dangerous pressure on the brain!

She underwent emergency surgery to relieve the pressure, then underwent a second surgery to replace the portion of her skull removed during the first one.