They're one of the most private couples in Hollywood, and recently welcomed a daughter despite the fact that nobody even knew they were expecting.

On January 2, Benji Madden and Cameron Diaz announced her arrival on Instagram, writing, “We are so happy, blessed and grateful to begin this new decade by announcing the birth of our daughter, Raddix Madden. She has completely captured our hearts and completed our family."

The post continued, "While we are overjoyed to share this news, we also feel a strong instinct to protect our little one’s privacy. So we won’t be posting pictures or sharing any more details, other than the fact that she is really really cute!! Some would even say RAD. From our family to all of yours, we’re sending our love and best wishes for a Happy New Year and Happy New Decade."

So, clearly they will continue keeping things private in the life of their new daughter, as much as they did with Cameron's pregnancy.

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Their Relationship Was Revealed In 2014

It was reported that the pair were introduced by Nicole Richie, wife of Benji's brother and Good Charlotte band mate Joel Madden.

The two had a whirlwind romance, getting married less than a year later, with a source telling Us Weekly, “Everyone thinks it’s wild but are so happy for them. Benji always tends to fall in love easily, but this time it’s for real and he landed a great girl."

The source continued, "They obviously both make each other incredibly happy and there’s nothing better than that.”

They Were Married In January 2015

Though they were married very quickly, it seems things were quite solid between the pair.

Cameron told Harper's Bazaar in 2016, “(Marriage) was the biggest thing I’ve done in my 40s, and it opened me up in different ways. It’s pretty awesome. I didn’t think it was something I’d do, and I don’t know if I’d have done it if I hadn’t met my husband. It was a surprise.”

Cameron has taken some time off from acting after their wedding, clearly needing a break after years of working non-stop.

A source told Us Weekly last summer, “She feels she spent so many years working a grueling schedule." They claimed she is very fulfilled in her life” and “very happy being away from acting," concluding "she just wants to have a slow pace and normal routine now. She’s loving this time in her life.”

She Enjoys Equality In Her Marriage

Speaking about equality in a relationship, Cameron seems to have found a winner in her husband, who is clearly supportive of her.

In 2017, she spoke at Goop’s Wellness Summit about this partnership, claiming, “We women are objectified so much. Somehow my husband has just been able to kind of show me what it’s like not to have that be a part of a relationship, and being an equal."

She continued, " I never experienced that before. I’d never been loved in that way. I look at him every day and he inspires me — he works so hard. I feel so lucky.”

The Couple Have Frequently Gushed About Each Other

The couple appear incredibly happy, constantly gushing about each other and how happy they are in their marriage.

Benji posted on Instagram in 2017, “I don’t think anyone could ever know the Depth, Kindness, and Compassion that I get to experience everyday thanks to My One and Only – You got me til the end baby."

Cameron has expressed similar sentiments when she spoke to Andy Cohen in 2016, claiming nobody compared to her husband after she was asked to speak about her exes.

She said, “Everything else just washes and slips away. Oh, right, this is what the real thing is. This is what real love is. This is what real commitment and devotion is. This is the person you build your life with.’ … And I know that this is special.”

Now that they've grown their family, it appears they are happier than ever.