The 51-year-old "Our Brand Is Crisis" star welcomed new daughter Laila, a 3-year-old from Louisiana, who now joins son Louis, 5. Laila was previously in foster care.
"When I look at Laila, there’s no doubt in my mind that she was supposed to be here," Bullock told People magazine.
Bullock, 51, added that her son "spearheaded this whole journey" and that the two kids are already close.
"My family is blended and diverse, nutty, and loving and understanding," Bullock told People. "That's a family."
Here's a quick look at Bullock's path to parenthood:
Bullock kept Louis a secret to keep him from being pulled into the middle of the madness but seemed to hint at her new bundle of joy while accepting the Academy Award for best actress. "I had to smile at the parallels," she told People in 2010. "Here I was promoting a story about a family who adopted a son, and here we were having done the same thing."
But before she could go public with the adoption, Bullock's marriage to James implodes and she files for divorce and decides to raise Louis as a single mother.
Bullock decides to raise Louis in Los Angeles as well as Austin, Texas, so he can "see every color under the sun." Like all parents, she admits to feeling moments of self-doubt.
"Every single second of every single day ... don't know if I feel like a bad mom, but at the end of the day I'm always plagued with, 'Did I do enough? Should I go in a different direction?'" she told Parade magazine in 2013 "But I also know that my entire life revolves around Louis."
After being named People's Most Beautiful Woman, Bullock reveals that her role as mother makes her feel most beautiful.
"Everything I’ve learned about love I’ve learned from Louis, and that there is no such thing as being done loving. We have a lot of it," she told People.
She also dispels rumors that she is getting a sibling for her son. "At this time the only kids in my house, other than Louis, are the ones whose parents want them back at the end of the playdate. But if these drumbeaters know something that I don't, I'd appreciate a heads-up on the details so I can pick up some supplies. I'm wickedly unprepared if Louis is getting a sibling this week," she said.
Indeed, Bullock is already fostering Laila from Louisiana but keeps it under wraps for fear that the adoption might not be finalized if revealed too early. The star reveals to People that son Louis actually spearheaded the process three years earlier.
"In this lifetime we are lucky, because we can make the family that makes us happiest,” she told the magazine. “And sometimes you just need to go out and find it and bring it home!"