The 51-year-old Australian actress discussed 25-year-old daughter Isabella Cruise and 23-year-old son Connor Cruise in a new interview with Who magazine.
"I'm very private about all that. I have to protect all those relationships," she told the publication. "I know 150 percent that I would give up my life for my children because it's what my purpose is."
Kidman adopted Isabella and Connor during her 10-year marriage to Cruise, from whom she split in 2001. Isabella and Connor follow Cruise's religious beliefs and practice Scientology.
"They are adults," Kidman said of the pair. "They are able to make their own decisions. They have made choices to be Scientologists and as a mother, it's my job to love them."
The Big Little Lies star said she has unconditional love for Isabella and Connor despite her differing beliefs.
"I am an example of that tolerance and that's why I believe -- that no matter what your child does, the child has love and the child has to know there is available love and I'm open here," Kidman said.
"I think that's so important because if that is taken away from a child, to sever that in any child, in any relationship, in any family -- I believe it's wrong. So that's our job as a parent, to always offer unconditional love," she added.
Kidman previously discussed her "unconditional love" for Isabella and Connor in an interview with Town & Country after playing an adoptive mother in the 2016 movie Lion.
"I relate to that," she said. "It's not about anything else other than 'I wanted you.' It's that deep and personal, and whatever your journey is, I'm here to love and support you. That's what I connected to."
The actress had nothing but praise for Isabella and Connor in an interview with Women's Weekly in 2014.
"They are generous, kind and hardworking," she said of the pair. "And these are traits that I love to see in my children."
Kidman is also parent to two daughters, 10-year-old Sunday and 7-year-old Faith, with husband Keith Urban. She recently told New York Magazine her marriage to Cruise "cocooned" her from sexual harassment during her early career.