There are many possible outcomes on two cases. The court will decide if California's ban on gay marriage is unconstitutional. The justices are also expected to rule on whether married same-sex couples can receive federal benefits.
Jason Howe is a married father of 1-year-old twins, Olivia and Clara. He's hoping the Supreme Court decisions on the Defense of Marriage Act and Proposition 8 will have positive outcomes for same-sex couples.
"Our children deserve to know that their family isn't second rate, that their parents are recognized just like anybody else's parents," said Howe.
Howe and Adrian Perez are one of the 18,000 same-sex couples married in California when it was legal. But they have to file separate federal income tax returns and their marriage is not recognized in many states.
Loyola Law School professor Jessica Levinson says the court could strike down DOMA, denying federal benefits to couples where same-sex marriage is legal.
"Unless there's a very broad Prop 8 ruling that says same-sex marriage is now legal and then DOMA will have a serious effect in every state," said Levinson.
Another possibility is that the justices could decide Prop 8 supporters did not have legal standing to appeal, and allow a lower court decision invalidating Prop 8 to stand.
"The district court ruling striking down Prop 8 would stand, so that would be the final ruling for. And then that's the question: Is it just Alameda and Los Angeles, where the two plaintiffs reside? Or is it going to be broader, is it going to be all of California?" said Levinson.
Prop 8 supporter Randy Thomasson, of the group Save California, hopes the marriage ban is upheld, but he expects more legal challenges.
"Democrats that rule the state legislature are already planning to use their power to undo the vote of the people if they possibly can on marriage," said Thomasson.
Jeff Zarillo and Paul Katami of Burbank, two of the plaintiffs in the Prop 8 case, will be in Washington D.C. when the rulings come down. They'll head back to Southern California for a Prop 8 event Wednesday night in West Hollywood.