Matthew McConaughey says it's "nobody's business" why he and Camila Alves haven't married.

The "Lincoln Lawyer" actor has two children with the Brazilian model -- Levi, two, and 14-month-old Vida -- and while the couple are very happy together they have decided not to marry, for reasons Matthew wants to remain a secret.

He said: "Would I like the perception of me to be a true mirror of who I am? Sure. Absolutely. Are there still things that I've got that are mine? That are nobody's business? Speculate all you want. Why didn't Camila and I get married? Nobody's business." However, while they are not man and wife, Matthew, 41, wanted 29-year-old Camila to feel secure in their relationship as soon as they realized it was serious so he made sure they bought a new home together.

He told America's Esquire magazine: "Before this, I had a super home in the Hollywood Hills that I did by myself -- landscaping, detailing, pretty much everything. But that house was mine. And yeah, we coulda gone in there right away. Camila would have said, 'Fine, don't change a thing.' But I thought, I found the woman I wanna do it with, the woman I wanna make a family with, hopefully live our life out together.

"She needs to have 50 per cent of that. I mean, it's a lot easier for me to be at 100 per cent. I'd always been 100 per cent. It's braver for me at 50 per cent."