Moon phase compatibility for friends and family
Moon phase compatibility for friends works the same way it does for couples, because the calculation only ever sees two dates, but a few parts of the reading land differently once romance is not involved, and one part of it is genuinely different for siblings.
What carries over unchanged
Nearly all of it. The pairing readings describe tempo, who starts, who finishes, who needs to talk something through, who needs to sit with it first, and none of that is specific to a romantic context. A square between two colleagues produces the same argument about timing that it produces between partners. Two Waxing Gibbous friends will still miss a deadline together because neither will call the thing finished.
In working relationships the tempo reading is more useful than in romantic ones, because a project has explicit deadlines and a relationship does not. Knowing that a collaborator sits a quarter-cycle away from you predicts the specific disagreement you are going to have about when to ship.
What changes
- Opposite pairings lose their charge. New Moon with Full Moon is described as magnetic in couples material. Between two friends it usually reads as an unusually effective division of labour (one starts things, the other reads the room) without the intensity the romantic version describes.
- Exit options are different. Friends and colleagues can see less of each other when a square gets tiring, which quietly resolves a lot of friction that partners sharing a household have to actually address.
- Family relationships cannot be exited at all. That makes the conjunct pairing (same phase, same blind spot) harder in families than anywhere else, because the outside corrective the pairing needs has to come from someone who is not in it.
Siblings are a genuinely special case
For most pairs of people, birth moon phases are effectively random relative to each other. Siblings born close together are the exception, and the reason is arithmetic rather than astrology.
Because the phase cycle repeats every 29.53 days, two siblings whose birthdays are separated by a whole number of lunations share a phase. An age gap close to a multiple of 29.53 days, or close to a whole number of years, since 12.37 lunations fit in a year, makes matching or near-matching phases more likely than chance for narrow gaps. A gap near half a cycle from a multiple puts them opposite. For siblings several years apart the effect washes out entirely and the pairing is as random as any other.
Worth knowing, because families sometimes read significance into two siblings sharing a phase when the explanation is that they were born fourteen months apart.
Parents and children
The framework offers nothing specific about generational relationships, the readings were written for peers, so a parent and child pairing has to be read as the tempo description it is, with the obvious caveat that the power balance is not equal. A First Quarter parent and a Last Quarter child are not two colleagues disagreeing about pace; one of them decides. That asymmetry is not in the readings, and it matters more than the pairing does.
Running it
The calculator takes any two birth dates and has no idea what the relationship between them is, so it works unchanged. The full chart is written for all 36 combinations rather than for couples specifically. For the general framework behind all of it, see what moon phases are said to mean in relationships.