You can use your natal chart to see many different things in your life. You can map out your personality, and you can assess different areas of your life and what they hold. But you can also use your natal chart to see the other people in your life!
The other people in your life & astrology
In general, the 7th house governs the people in your life and your relationships, but this is an umbrella position that everyone else falls under. The 1st house, which exactly opposes, is the house of the self, so of course, the opposing house, the 7th house, rules others.
But each of the houses govern a different person who is in your life specifically, so while you can default to looking at the 7th house in general, it only gives you an overall picture.
Signs on the cusps and plans in the house can give info about the specific people you attract with that house, and you can actually use transit aspects and progressions involving that house and the planetary ruler of that house in your chart to map out what could be coming for each person predictively using your own chart.
This can be helpful when someone in your life doesn't have a known birth time but you do (and you can use it in reverse if you don't have a known birth time but others in your life do, you can use their natal chart and transits to track potential impact on you!).
The Houses in Astrology & Other People
So let's review which people in your life are governed by which houses in astrology:
1st house: this is the house of the self, so it governs you in general; also one of your grandparents (the parents of your 10th house parent)
2nd house: this is the only house that isn't really assigned to anyone except perhaps those you deal with in a financial sense (though that usually falls under the 8th house)
3rd house: your siblings, cousins, neighbors, young people in your life (that are not your children), your students (those you teach)
4th house: your parents (usually one parent each is assigned to the 4th and 10th houses; it's said the dominant parent is the 4th house parent)
5th house: those you're dating, your children
6th house: your co-workers, your employees, aunts and uncles from your 4th house parent
7th house: all others in general, but also specifically your committed partner (spouse, even common law), your "open" enemies (the ones you know about), one of your grandparents (the parents of your 4th house parent)
8th house: mutually beneficial partners (usually financial)
9th house: your grandchildren, your in-laws, your lawyer, stepchildren, your teachers
10th house: your parents (one is 4th house and the other is 10th house), your boss, your mentor
11th house: your friends, those you are in a group with, adopted children
12th house: your "closed" enemies (those you don't know about), your spiritual guides, aunts and uncles from your 10th house parent
Suggested Reading: Intro to Astrology Houses