An ABS-CBN News source said on Friday that Aguilar converted to Islam six months ago to marry his girlfriend.
A Philippine Daily Inquirer report said Maguindanao Governor Esmael Mangudadatu will stand as principal sponsor.
Meanwhile, Aguilar is now facing qualified seduction charges over his relationship with his minor girlfriend.
In a previous interview, Aguilar said he will face the charges.
The couple earlier said they are planning to wed in two years, when the girl turns 18.
Aguilar also openly shared their plans of building a family of their own.
The singer’s girlfriend is turning 17 on November 29.
Aguilar, who separated from his third wife a decade ago, has six children.
His youngest, named Jeriko, is 24 years old.