People either born on 3, 12,21 or 30 OR on Thursdays or in December or March are primarily ruled by Number 3= Jupiter.

This planet gives, command, control, love for discipline and ethics but at the other end could make one dictatorial or too bigoted in opinions (religiousness gone to extreme).
In Vedic Astrology parlance- Jupiter is also called Brihaspati.

Jupiter is said to be the law maker- the person who lays down law- people influenced by this number want laws/rules- hence could make many enemies in the process. Jupiter is karaka/signifactor of 5^th and 9^th and also 2^nd house- so it does represents children, wealth flows, dharma and luck.

In true sense it’s the planet of expansion. It is a planet for friendships, socials and well being.

People influenced by Jupiter are generally ambitious and warm, but may be careless about money. They invariably are at the top- but in doing so they might stress their nerves.

Aspects of Jupiter:

Jupiter aspects with maximum energy the houses, 5^th, 9th and 7^th from the place it is placed in your horoscope.

Unless ruling a malefic house ( 6^th/8^th or 12^th), Jupiter is a great benefic and make you blessed!

You Are Ruled by Planet Jupiter   if:

If you are born on 3,12,21,30 or Thursdays. Or Jupiter is strong in your chart or your ascendant or moon sign is Sagittarius or Pisces.

How to Check How Strong is Jupiter  in Your Horoscope : 

See how your Thursday or dates 3,12,21 or 30 go. Do you make good money, or you have good friends, you have great compassion and love for nature or you like conventions- then you might be a jupiterean.
Your health : Nerves need to be taken care of so is liver and basic digestion. Skin has to be kept healthy with exercise.

Your Lucky Colour : All shades of Violet or purple
Your Lucky Stone : Yellow sapphire or topaz.

Your Lucky Jupiter Mantra(sacred Incantation):
OM BRIM BRIHASPATAYE NAMAHA 108 TIMES.

Your Lucky Jupiter Yantra(Amulet):

 Interesting Facts:

Note 9= 3×3 and 12=3×4, so one can clearly see that pure Jupiter value are in the Sign Sagittarius(9^th sign = 3 x 3= Jupiter X Jupiter) , which is followed by the mental sign of Jupiter, that is Pisces( 12^th sign = 3×4 = Jupiter X (Rahu or Uranus)), causing Pisces people being insecure about money(Rahu/Uranus  causes insecurity in minds- especially for money)- but rest of the Pisces qualities are mostly same as Sagittarius, as both are ruled by planet Jupiter.