There are the rings on their fingers, of course. Then there's London's daughter Cooper, 15, from his first marriage – she's got a new stepmom in Karstens.
But the big news in the newlywed household? "I got a new tax deduction," London, 38, best known as the ambivalent quarterback in Dazed and Confused, joked to PEOPLE.
Just over a week after he married Karstens, 35, in North Hero, Vt., the bride's hometown, the couple are settling into married life in L.A. and, reports London, "It's been wonderful."
"She was my best friend for a very long time," he says. While shooting a movie in 2009, "I just couldn't stop thinking about her. I didn't even realize that I was in love with her."
The couple first met in 2008 through London's twin brother, Jeremy London, who made headlines last summer when he was kidnapped at gun point and forced to use drugs (one of his kidnappers in the bizarre abduction eventually pleaded guilty in March).
Although Jeremy, who unsuccessfully filed a restraining order against his brother last June, was unable to attend the wedding, Jason says the ordeal is behind them.
"God bless him," Jason says of his brother, who was making his directorial debut the weekend of the wedding. "He's doing great now. We were all there for him during the beginning of all that. [Karstens] was a great support for him, and it was a tough situation – but we got through it."
Their Fairy Tale
Although his brother couldn't be there for his big day, London says he and his bride had plenty of company to help them celebrate – 140 people, to be exact.
"I was in a daze. I couldn't believe it was mine," he says of the wedding ceremony, which was held at Karstens's family home. "It was a fairy tale."
The bride wore a strapless Judd Waddell dress as she and London exchanged vows they wrote themselves. They also mixed wedding traditions – such as the Jewish custom of stomping on glass – with their own twists, such as their newlywed duet to Rascal Flatts's "Bless the Broken Road."
"I'm not a mushy guy, but I was really mushy that weekend," says London. "I wish we could have slowed down time a little bit. It goes by so fast."