"It was the first decision I made as a father," Aiken, 29, tells the upcoming issue of PEOPLE, on newsstands Friday. "I cannot raise a child to lie or to hide things. I wasn't raised that way, and I'm not going to raise a child to do that."
Aiken says he expects the news may overwhelm some of his fans. "Whether it be having a child out of wedlock, or whether it be simply being a homosexual, it's going to be a lot," said Aiken, who returned to Broadway last week as Sir Robin in Monty Python's Spamalot.
He adds that he hopes his fans "know that I've never intended to lie to anybody at all. ... But if they leave, I don't want them to leave hating me."
How He Came Out to His FamilyThe born-again Christian singer also reveals how he told his mother Faye he's gay four years ago. After dropping off his younger brother Brett, who was being deployed to Iraq, at Camp Lejeune, "I started crying in the car," Aiken remembers. "It was dark. I was sitting there, thinking to myself. I don't know why I started thinking about it ... I just started bawling. She made me pull over the car and it just came out."
So what was his mom's reaction? "She started crying. She was obviously somewhat stunned. But she was very supportive and very comforting." Even now, Aiken admits, "She still struggles with things quite a bit, but she's come a long way."
As for his own child, Aiken tells PEOPLE that Parker – who was conceived via in vitro fertilization with his best friend, music producer Jaymes Foster – will be raised in an environment that is "accepting and allowing him to be happy."
Says Aiken: "I have no idea if he'll be gay or straight. It's not something I'll have anything to do with, or that he'll have anything to do with. It's already probably up inside the code there ... No matter what the situation you're in, if you're raised in a loving environment, that's the most important thing."
For the first photos of Parker and more of Clay's deeply candid interview about fatherhood, coming out, and his message for the Claymates, pick up the upcoming issue of PEOPLE, on newsstands Friday.