Meta Platforms Inc (META)

[Fastmandoo]

Zuckerberg's Facebook options are a different story, however. Although he already exercised 60 million of his 120 million stock options in conjunction with the IPO, he is still sitting on the other 60 million. At the offering price of $38 a share, he could net about $2 billion when he exercises those options down the road. (Facebook is currently trading about 10% below the IPO price.)

0:00 /1:24Exclusive: Candid 2005 Zuckerberg video
Depending on when the options were granted and when they will be exercised, there is now a community property interest, which means that, as his wife, Chan could stand to benefit substantially if Zuckerberg makes another bundle on those options in the future.

Unless, of course, there is a prenuptial agreement in place safeguarding his Facebook fortune, which Anteau says is likely.

"If he came in to see me, there's no question he would be getting a premarital agreement," he said.

Facebook's new billionaires
Those legally-binding contracts, which are drawn up by an attorney, protect each person's assets and determine support obligations in the case of a split. They can be particularly valuable if the division of wealth between a couple is grossly uneven prior to the marriage, according to New York matrimony attorney Barry Slotnick, who represented Melania Trump in her prenuptial agreement with Donald Trump.

Billionaire or not, Lauren Lyons Cole, a certified financial planner in New York, recommends that all couples talk openly about money before tying the knot. Prenups get a "bad rap" she said, but they can open the door to a lot of necessary conversations.