They've kept it on the down-low, but Zac and Vanessa are going to get hitched!

They may still be young, but Zanessa have committed to each other forever and ever, and we couldn't be happier for them - even though we can never marry Zac now...boo!

Zac reportedly proposed to Vanessa during a trip to Japan in late January and they've kept it quiet ever since...aww!

An insider close to the couple said: "Zac is relieved to be out of the pressure cooker, because Vanessa's mom has been putting serious heat on him to make an honest woman of her daughter.  She is old-school and doesn't approve of Vanessa living with Zac without some type wedding promise."

He added: "Zac really loves the current arrangement.  He adores Vanessa and they gel really well together.  Gina [Vanessa's mother] already considers Zac part of the family, so she's happy that he proposed."

Even though the couple have been living together, we're glad Zac is being the perfect gentleman, and Vanessa must want to spend the rest of her life with him otherwise she wouldn't have said yes!  Wedding bells soon, perhaps?

So, is it the most romantic thing in the world for the young lovebirds or should they wait until they're older to get engaged?