Us Weekly was the first to report the news last week, but Priscilla Presley has confirmed it to "Entertainment Tonight."
"She wanted it really to be kept a secret for a long time, you know, and I think women should, because they should be able to announce what they're having and when it's time to make the announcement," the elder Presley told "ET."
Lisa Marie Presley's father, Elvis, was a twin, and Priscilla has younger twin brothers, Usmagazine.com noted.
The babies will be the first children for Lisa Marie Presley and her fellow singer and husband of two years, Michael Lockwood.
Lisa Marie Presley also has two children from her previous marriage to Danny Keough.
She will soon be one of the latest celebrity moms to experience a double birth. Angelina Jolie, Jennifer Lopez and Julia Roberts have all recently welcomed twins.