Originally Posted by ladyslipper
But I don't think you have to be bi to be with the same lady at once... ?
No, that was in case you were looking for a relationship in which all three of you would be involved all at once, which is generally what's understood by "triad". What you do want is referred to as a "vee" or "V", with you as the hinge or pivot, meaning you would be involved with both of them but they wouldn't be directly involved with one another, only through you.
Some men might be uncomfortable with the idea of being close to another man while having sex, but a lot of them probably wouldn't, and really the only way to know is ask him!