(Cover) - EN Showbiz - Anna Paquin and Stephen Moyer consider themselves to be married, even though they have yet to exchange vows.

The True Blood co-stars got engaged in 2009 and are expected to wed later this year. They are keeping the details of their ceremony secret, but say they aren’t making too big a deal out of tying the knot because they already feel like they are married.

"We pretty much consider ourselves married now, even though we aren't yet. Doesn't it make you a little sick in your mouth?" Stephen joked in the September issue of Rolling Stone magazine.

Stephen, Anna and their co-star Alexander Skarsgård appear nude and dripping with blood on the cover of the US publication. Inside the magazine, Stephen opens up about why he thinks True Blood and other vampire stories have been so successful in recent years.

He thinks vampirism and sex are intimately linked, and sees the act of sucking someone’s blood to be deeply erotic.

“If we go from a base level, vampires create a hole in the neck where there wasn’t one before,” Stephen explains. “It’s a de-virginisation - breaking the hymen, creating blood and then drinking the virginal blood.

“And there’s somethin sharp, the fang, which is probing and penetrating and moving into it. So that’s pretty sexy. I think that makes vampires attractive. Plus, Robert Pattinson is just hot, right?”

Robert plays vampire Edward Cullen in the hit Twilight film franchise. (C) Cover Media