Despite welcoming a child and marrying Alicia Keys, Swizz Beatz' honeymoon is over ... and he's getting hit with a lawsuit.

According to reports, the producer has been slapped with a $1.5 million lawsuit by a songwriter who claims he co-produced the hit single, "My Drink N My 2 Step", by Swizz' recording artist Cassidy.

Antwann Frost claims he got stiffed on royalties from the 2007 club banger.

In court docs, Frost claims that Swizz assembled the drums while he created "all of the other original musical components that shaped and defined" the song.

Soon after the track was released, he says the producer paid him $5,000 and gave him a 5 percent ownership over the song, while he and Cassidy split the other 95 percent.

However, Frost says he rejected the offer. And, is now suing to acquire what he feels is rightfully his -- according to the suit, an equal percent of ownership in the song.

In recent months, Swizz Beatz has had other legal problems in addition to this one. Back in May, his divorce from singer Mashonda was finalized and a month later, he settled with a $334,000 payment to his ex for unpaid child support payments and alimony.

In July, reports stated that Swizz owed $2.2 million to the IRS and New York State. His attorney said they are currently working with Uncle Sam to get the debt settled.

"We have been discussing the issue with the government for years and are currently negotiating an amicable resolution of the dispute," said Swizz's attorney.

Source:BallerStatus