Families have astrological similarities just like they have genetic likenesses. Family charts reveal amazing synchronicity.
Two sisters have Sun-Saturn aspects: big sis has the conjunction, little sis the opposition. Both are achievers with graduate degrees and professions, and responsibilities within the family hierarchy. Their mother, a Capricorn whose Sun is sesquiquadrate Saturn [its own ruler], has described the two as "my delayed twins" because of their similarities. Sun-Sat. natives are long haul people. They have common sense, bedrock values. They're the designated drivers of life.
Big sis' Sun conj. Saturn has Jupiter sq. the conj. Her sibling has Jupiter trine Saturn and sextile the Sun. Each has Mercury in the 3rd house.
Big sis has Mercury conj. Pluto.
Little sis has Mercury conj. Mars.
Both women are gabby, friendly, car-fixated; both are public speakers.
Mercury in its own house  gives natural ability and strengths in speaking, short journeys, siblings, neighbors, and manual dexterity.
Even more these strong Mercury placements tell the true story of how the sisters get along or rather how they don't. One relative called the two the worst case of sibling rivalry she'd ever seen.
With each sister having a conjunction of the planet of communication from a Scorpionic planet [Mars, the traditional ruler, and Pluto, the newer ruler], barbs fly back and forth.
Mercury is neutral and takes its cue from the planets aspecting it. Mars and Pluto rule aggression and dominance respectively. Like Israel and Palestine, the sisters have periodic fall-outs. As each fulfills familial duties, they have learned to keep their distance and watch their tongues to get along.
Emotionally, the diplomatic breakthrough often comes from their brother who also has Sun conj. Saturn. But here's the difference. He has an exact [partile] conjunction of Sun and Venus at 5.9 and 5.12 degrees Cancer. This is called combust when the planet is this close to the Sun. Its effect is to "combine the planet's influence more closely with that of the Sun, until it is no longer a physical emotion capable of independent control, but an integral part" of that consciousness that the Sun imparts; Venus combust the Sun is also reputed to give nymphomania [Astrology Encyclopedia]. Interestingly the brother has admitted to going through such a phase in his youth.
But since he has Sun conj. Saturn [0 degrees Cancer], over time he transmuted that quality to being the person who conciliates [Venus]--in his job and within his family. That's a nice way of saying he sublimated his excessive sexual energies.
His Mercury [29 degrees Gemini] is closely conjunct this Saturn: What a genetic pattern--Mercury again conj. an outer planet. This family has gabfests of the highest order, and they all have 3rd/9th house occupations [teaching, the law, driving]. But luckily for all, the brother's Sun/Venus/Sat/Merc. conjunction is a stellium or concentration of three+ planets in the seventh house.
The seventh house rules partners, enemies, contests, public battles, marriage. The brother, who has been married for 35+ years, is the calming force between the sisters.