Prince may have gone on to become an iconic music legend, but his sister, Tyka Nelson, established a music career in her own right – and with no help from her superstar brother.
Prince, 57, and Tyka, 55, grew up with a knack for music, thanks to their parents John Nelson and Mattie Shaw. But one of Tyka's publicists, Al Gomes, tells PEOPLE that the two made a deal as kids, one that would define their relationship for years to come.
"She was really, really happy with her album," Gomes says of Tyka's most recent record A Brand New Me, noting that he urged his client and friend to share the new music with her superstar brother.
"She said 'No.' She said, 'I don't want to bother him. We have this thing we discussed when we were kids,' " Gomes recalls. "I said, 'What?' And she said, 'We promised each other that if one of us made it big the other one wouldn't come to them for help.' "
He adds that Tyka would have done the same thing had she hit it big – "They had that pact and they kept it."
The new details about the special relationship come as Tyka, Prince's only full-blooded sibling, has filed an emergency petition requesting that a special administrator be appointed to oversee the star's estate – valued at an estimated $250 million and expected to increase by another $100 million in the coming years.
Tyka declared that there is no known will for her superstar brother, a fact confirmed by PEOPLE on Monday. She also named herself and five living half-siblings as potential heirs to the fortune.
Gomes says he continued to urge the musician to call Prince.
"I said, 'Call your brother, not as Prince, but as a brother…' " he says. "And she did eventually and told him that she released an album."
"I think they were in touch throughout the years, but they made a pact not to bother each other when it came to their careers."
According to a 2008 interview with City Pages, Tyka began writing songs when she was 10 and hasn't collaborated with her brother since they were young.
She plays four instruments, piano, bass, guitar and clarinet and has released six albums.
Tyka told City Pages that she and Prince had a strained relationship – "My brother, he just thought I was crazy."
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Prince was found unresponsive in an elevator at his Paisley Park compound in Minnesota last week. Details surrounding his cause of death have not been released.
In the days following Prince's death, speculation about who will take control of his estate – which experts say could be valued at upward of $250 million – and it appears that Tyka is the most likely candidate.
Despite their strained relationship, it was Prince who entered Tyka into a rehab program in the early 2000s, she told The National Enquirer. She said she battled addiction to cocaine and prostituted herself to support her children.
Gomes says that when Tyka came to him four years ago seeking help with promoting her album, she was in a different place.
"She explained to me from the start that she had conquered a lot of stuff. At the time she was very much at peace with her life because she had faced and conquered evil," he says. "Her music helped her push through the hard times in her life."