Johnston and Palin, the 19-year-old daughter of former GOP vice presidential nominee Sarah Palin, recently told Us Weekly they are engaged again, but they don't have the blessings of their families.
Levi, 20, is the father of the younger Palin's 18-month-old son, Tripp. The couple called off a previous engagement shortly after the child was born in December 2008.
Mercede Johnston, Levi's sister, told TV's "Inside Edition" in an interview to air Thursday that her family found out about the engagement through the media.
"You would think that a normal family would call you and say, 'We're getting married.' We found out through the media, which is heartbreaking and rude," Mercede told the program. "I would love to be invited. I would love things to be put in the past. … But in all honesty, I don't think they're going to invite us. Wouldn't even tell us the date. It broke my mom's heart."
"I would be absolutely devastated if I wasn't invited to the wedding -- it would be the last straw," Sherry added on "Inside Edition." "They should elope if they can't have the Johnstons and the Palins together. But don't leave us out of it. That would kill me."
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