Matthew McConaughey once turned down a threesome with two sisters - because he didn't want bad karma.The 'Sahara' star - who has dated a host of Hollywood beauties including Sandra Bullock, Ashley Judd and Penelope Cruz - refused to have sex with the two women because they were both already taken and he didn't want any spiritual comeuppance from the romp. He revealed to Loaded magazine: "Two sisters once offered themselves to me. But they weren't single and one wanted to get away from her husband. I don't jive with that. You don't sleep with someone's lady if they're married because it will return and bite you in the ass. "McConaughey also believes honesty is the key to any successful relationship. He added: "I hide nothing. If you hide something and the relationship starts going good, whatever you're hiding, it's coming out. Better to get it all out on the table and say, 'That's what you're getting man.'"