Nope, I don't trust him, because we do have another person involved in our relationship, and he has gone behind my back. Both of them have lied to me in several ways. Overall, a rough, tough hard situation, that could spell disaster.
For instance, she'll say she's not happy in a situation where it will never be a normal relationship, then he'll say to her "Don't tell her, but, don't worry, I'll leave her for you." It's really depressing, because he wouldn't ever end our marriage, like he's said time and time again he just can't stand to be without me, but he also can't stand the thought of her leaving, or the thought of someone leaving him in general.
So as soon as she says she's going to leave, he lies to her. I don't know why she believes it anymore, because this same scenario has played out at least ten times ... always the day she tells him "oh, I can't do this situation, I love you, it's just me or I go..." I've told her just to tell me when he gets like that, and she's finally realized that it's all bull-sh*t. I have a hard time trusting her because she is so willing to tell him that she would take him all to herself.
We had also set a rule that sex with the "third" would only be when we were both in the room, and they have also broken that rule numerous times and lied about it.
He quickly realized that lies weren't going to keep me around, and luckily for the last several months everyone has actually been sticking to the rules, and not lying. I just can't stand dishonesty. Who knows ... but, I don't think I recommend trusting your hubby/wife/significant other around an additional person. Most people can't handle being trusted like that. Before I got married I dated several men, and I never trusted them to the level I allowed myself to trust my husband. I thoroughly regret trusting him that deeply. Let's just say at this point it takes ALOT to earn my trust.