Actually, Lee Lehman does advocate using the 5th house for lovers and non-cohabiting relationships. She also advocates using the 7th house for live in lovers and married couples.

When you think about it, using the 5th makes a lot of sense when you consider that in Medevial times, people didn't usually have casual boyfriends and girlfriend relationships as they do now. Each relationship was a prelude to marriage and engagements were considered as binding as a marriage. Therefore it would have made sense to use the 7th house in those circumstances.

This house was traditionally designated "marriage," but societal attitudes toward cohabitation following sex have changed! First of all, for large stretches of time in European history, the lower classes cohabited when they felt like it, without the benefit of Church or civil rites to sanctify the union. The elaborate rituals of marriage were reserved for the upper classes. However, those astrologers who catered to the upper classes have proved more successful; thus, our references and our lore on marriage and cohabitation follow the upper class ideal, which has simply been appropriated by the lower classes once overall living standards improved.

However, marriage in the upper class mode was arranged, had nothing to do with love, and everything to do with property and heirs. A proper delineation of the 7th House thus began with the question of whether the Native would marry. This consideration had nothing to do with such questions as: how relationship-oriented is the Native, but whether the Native had or could accumulate sufficient wealth to make marriage a reasonable result, or enterprise.

When the historical association between marriage and business is understood, the attribution of variations of the same thing. However, even so, it was understood that love was possible between partners - it just wasn't necessary.

A loving relationship is shown by a trine or sextile between the rulers of the 1st and 7th Houses, or planets therein.

One more thought. It is still quite obvious to think in terms of relationships being primarily 5th or 7th House in nature. For example, a relationship which is heavily sexual, with no merging of finances and without living together is unequivocally 5th, while a relationship with cohabitation and a greater or lesser degree of financial mingling is 7th in nature. It has become the custom of our society since the Sixties that relationships begin in the 5th, and then move to the 7th if the parties are willing.

Deb: Most of the widely recognised sources state that the ?other person? involved in a one-to-one relationship would be judged from the 7th house, regardless of whether the question is one of marriage or just getting a first date. Lilly?s opinion was that the 7th house is used to judge ?all manner of love questions ? whether man or woman, wives, sweethearts ??

Sue: The third house will always be transport whether we are talking about horse drawn carriages or cars. In the same way, the 7th house will always be used to denote the other person asked about including a romantic interest or a business partnership. We don?t use the 7th house for business partnerships that are life long and then use the 5th house for business partnerships that last a couple of years.

Sue: What she found was that instead of the outer planets having words that were similar in description to their inner planets, each of the outer planets had keywords most closely resembling Saturn.

Her conclusion was that all modern astrology had done was to add three more malefics, making modern astrology far more malefic that they accuse traditional astrology of being.

While I do not discount the value of outer planets entirely, they are of no value as significators as they do not rule any sign.