Exclusive Sneak Peek: Leah Remini Goes Up Against Her Sister on TLC's It's All Relative

There's always a certain amount of rivalry among siblings, but Leah Remini takes the family competition to a whole new level on the series premiere of her new reality series, Leah Remini: It's All Relative.

In this exclusive sneak peek from Thursday's episode (10/9c, TLC), Leah tries to "out daughter" her younger sister Shannon when it comes time to celebrate the birthday of their mom's dog, Sadie.

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There's just one snag: Leah's mom, Vicki, didn't invite Leah to the party! Does Leah even stand a chance? Find out how the situation plays out in the exclusive video below:

Leah Remini: It's All Relative premieres Thursday at 10/9c on TLC.