7th house Aries often suggests that relationships for you can be quite intense and involving.You can be very clear about what you want and are more than capable of taking the lead.
It could also be that these qualities are projected to your partner(7th); so your partner is the one who seems very bossy, one dimensional, assertive and "leading" the relationship in some way.
Having 7th house Aries means you have Libra asc. So, you often see yourself as someone reasonable, tactful and diplomatic whilst, on the other hand, many people that you collaborate with(7th) seem selfish, self-centered, brash, abrasive and competitive.
With Jupiter there, it could suggest that these qualities of Aries are exaggerated or given a heavy (often irritating)dosage.
Maybe these Sag Sun people you attract have placements that sit in your 7th house? If so, they could be further emphasizing the Aries traits of the 7th house.
But my guess is that they inhabit your 3rd house cusp of Sag. They start to take on the role of annoying siblings or the relationship between you and them has a very strong brother/sister quality about it.