Without having to think about this for a second: No, never.
I follow the idea that you should treat others as you wish to be treated yourself. I never had luck in love yet, but the moment I find the right girl for me I would hate it if other men would try to come between us. Hence I also don't want to commit that "sin" myself and come between two people already in love. It's just a simple principle. If she is in a relationship, don't try to tear them apart, you would not want it to happen to your own partner neither...
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Do what Thou wilt shal be the whole of the Law.
Love is the Law, Love under Will. And...
every man and every woman is a star
(excerpt from The Book of the Law - Aleister Crowley)
"Od lo avda tikvateinu" (excerpt from the Israeli hymn)