Sex first starts with the mind then, to the body. That is why to attract men nature has given breast which is immediately noticed when we see some female. For attractions, there are many other factors, but the physical look is the prime.
As I hinted that mind is first device which trigger sensual urge and this is governed by Moon. Next important ingredient is courage and physical strength to have a successful physical relation. The muscles and courage is governed by Mars. Hence, the Mars placement and its strength have to consider for such activities. Along with all these, the maturity and communication skill etc. are also needed.
To be précised I should say, Jupiter causes early maturity, Mars gives courage to take risk and chance, a strong Venus induces sensual urge to experience intimacy, and the Moon to compel us to think from heart and thus we involve in early adventure with sex.
Weak Venus, malefic Moon and bad Mars in the horoscope and also having wrong placement of 7th house lord, then it is possible that the person may experience sensual happiness only when society will provide opportunity and when he will feel safe.
If, there is strong positioned Sun, good Moon and Jupiter then person will be reasonable, and he will bother for his prestige and society. Such native will avoid such activities even he may be desirous.
The Venus with the Mars or Rahu or Saturn along with weak Moon and other bad yogas in the chart make the person to follow all the methods to satisfy his mean sexual urge and sooner they get opportunity they start experiencing sensual pleasure.
The placement of Jupiter in the 7th house or 1st house gives early physical and mental maturity and such natives experience very early sex. It is also observed that they may have relation with married person.
If, in teen age there is major period of Venus or Jupiter and sub period of planets related to 7th then also sexual experiences are possible.
The worst thing can be observed in few charts:
Before teens, if there is a major period of Venus or Jupiter ruling and that time there is sub-period of Venus or planets related to the 7th house.
There is placement or aspect of Mars, Rahu or other evil planets on Venus along with weak Moon.
Then few children may have sexual abused. Along with previous combinations, if Rahu ruling or sub ruling comes then it can be further damaging.
Planets are important to influence human mind, but the social systems and parenting also contribute in a greater way. There are some community and country where sex is not a taboo, but for many it is just opposite and this will also modify the affect of planets.R