Part of Siblings

The Lot of Siblings is taken from Jupiter and Saturn, and it is among the thinnest attested of the medieval parts, appearing in the long lists but with little accompanying instruction and almost no worked examples. Its natural home is the third house, which in the classical scheme carries brothers and sisters, short journeys and neighbours, and most traditional judgments about siblings are made from the house and its ruler rather than from the lot. Recording it here completes the set the atlas carries; it should not be taken to imply that the lot was much used. Where a technique survives only as a line in a list, the honest description is that it is attested rather than that it is established, and a good deal of the medieval lot literature is in that condition.

The choice of Jupiter and Saturn for both the Lot of Siblings and the Lot of Children in the sources that give them is not an error: medieval compilers built many different family lots from the same small pool of natural significators, distinguishing one topic from another by the order of the arc and by which planet was taken first, a method that multiplies distinct lots from a handful of planets but leaves considerable room for the topic-crossing confusion that modern readers, working from incomplete or garbled manuscript transmission, sometimes fall into when two apparently identical formulas are found attached to two different topics in different sources.

The day formula stored for this lot is Ascendant plus Jupiter minus Saturn. It uses the same two planets as the Lot of Children and uses them the other way round, Jupiter added and Saturn subtracted rather than the reverse.

That has a precise consequence. The two lots are equidistant from the Ascendant on opposite sides: whatever arc separates the Lot of Children from the horizon, the Lot of Siblings sits the same arc away in the other direction. They are reflections of each other in the Ascendant. An astrologer who has computed one has, without further work, computed the other.

The motion is the Ascendant's, again almost exactly, because Jupiter and Saturn between them contribute about three minutes of arc a day. One degree every four minutes, a whole sign in two hours, and no usable degree from an approximate birth time.

The Jupiter and Saturn elongation embedded in the formula returns to the same value at every conjunction of the two planets, about every twenty years, so everybody born within a few years of each other carries very nearly the same planetary component. As with the Lot of Children, the birth time supplies essentially all of the individual variation, and the doctrinal reading of the lot as describing a person's brothers and sisters rests on a quantity that a whole birth cohort shares.