A planet of faith in things
Jupiter stands for growth, optimism and the beliefs that give your life some shape. It spends about a year in each sign, so people a few months apart in age often share it. It’s less a description of your personality than of where you feel lucky and what you trust will work out.
What it feels like from the other chair
When their Jupiter touches a personal planet of yours, you tend to feel larger around them. If it touches your Sun, you feel more confident. Touching your Moon, it can feel like being forgiven in advance for your moods. On your Mercury, it might be the friend who keeps sending you to bigger ideas and better books.
This is one of the more pleasant contacts to have, and that’s where the risk sits. Jupiter encourages. It isn’t known for checking the numbers. Two people lighting each other up can talk themselves into the business, the puppy and the cross-country move in a single weekend.
Also watch for imbalance. If one of you is always the one being expanded and the other is always the one doing the expanding, the giver can get tired, and the receiver can stop noticing.
Beliefs in the long run
Jupiter also speaks to philosophy: what you think a good life is, how you feel about faith, what you’d want to teach a child if you ever raised one. These things rarely come up on a second date, and they matter by year three. If your charts show Jupiter in tension with something personal, treat that as a nudge to have that talk earlier.
A useful test for this planet: are you both better people around each other, or just more excited? Both are nice, and only one lasts.