KING is a true underground success story, even if it does include some help from Prince.

Anita Bias and twin sisters Amber and Paris Strother gained all sorts of celebrity attention for their 2011 EP “The Story,” even landing an opening slot for Prince and testimonials from Questlove and Erykah Badu. Luckily, their debut, “We are KING” (KING Creative), was worth the five-year wait.

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Like the songs from “The Story,” which all appear here in extended form, “We are KING” is a combination of sweet soul harmonies, synth-driven R&B and laid-back cool.

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“Red Eye” is like a Janet Jackson ballad hijacked by an alt-R&B groove-maker like How to Dress Well. The first single, “The Greatest,” a tribute to Muhammad Ali that oozes with style, mixes shimmering ’80s-styled synths with ’90s R&B girl group attitude. And they even throw in some Tom Tom Club references.

The closing “Native Land” shows KING at the peak of their powers, all cooing vocals, spare instrumentation and a search for their future. It works impeccably well, suggesting that KING’s reign may be a long and prosperous one.