Tell the person that you are in a relationship that you don't want to be and go out with the other person.

do you love this extra person or are you infatuated? is it lust? is it worth hurting the person you are in the relationship with? do you love them? are you in love with them? is the relationship worth something, i.e., is it worth saving it where possible?

if your answers are: no, infatuated, lust, no, yes, yes, and yes; then ignore new person.

if the answers are different, leave the whole thing on the hob for a while and see how both sides develop (relationship may improve, new person might b***** off).

don't cheat. if you have already cheated on the person you're in a relationship with, then you are probably gonna have to 'fess up at some point.

either which way, we make our own beds, and we have to lie in them.

well you can't be in two places at once, choose one or none.

if u aint serious about any of the relationship and just want some fun, be a two timer

but if you are reallly serious, stay in 1 relationship. perhaps you want to make the other person your friend?