Ozzy Osbourne has reportedly promised his daughter Kelly he will be "clean" by the time she gets married.
The famous family has been shaken by Black Sabbath rocker Ozzy's renewed battle with addiction.
Kelly is happily dating vegan chef Matthew Mosshart and with rumours the pair got engaged at the end of last year, the Fashion Police star is apparently putting pressure on her dad.
"Kelly's using a little blackmail to help her father get clean sooner rather than later. She knows he has to want it, but she thinks a little tough-love encouragement can't hurt," a source told RadarOnline.
"Kelly went right for daddy's heart – she made it clear that she needed him to be present when he walked his little girl down the aisle. Ozzy would never ruin her big day, so he promised Kelly that he would get it together way before her wedding to Matthew."
Ozzy's wife Sharon has apparently moved out of their family home while he gets his act together.
Despite rumours they were heading for a divorce, the pair have so far denied they plan to part ways for good.
"Ozzy knows better than anyone that he can't sober up for anyone except himself," the insider continued.
"But he says he's motivated by the fact that Sharon left him and now he's promised Kelly that he would walk her down the aisle only if he's clean. Kelly even threatened that if he wasn't coherent by the time of the wedding that she would have her brother Jack give her away."
Both Kelly and Ozzy are currently spending time in Australia.
The singer is performing, while Kelly is promoting her new column for the country's Cleo magazine.