Nuclear kin have chapters. Parents, brothers and sisters, marriage and children each get one in the Tetrabiblos, and the medieval catalogues give each a house of its own. Uncles, aunts and cousins get neither. They are read, but they are read by extension, and the extension is what makes them worth an entry.
That has two consequences for anyone using this one. The first is that the reading is only as sound as the parental house assignment it starts from, and that assignment is itself disputed. If the fourth is the father then the paternal uncle is the sixth. If a reader follows the modern convention and takes the tenth for the father, the same uncle moves to the twelfth. The disagreement about the parents propagates outward into every relation derived from them.
The second is that the further a relation sits from the native, the thinner the signal a chart carries about it. Traditional practice treats this as a matter of degree rather than a hard boundary: a chart is most eloquent about the native, informative about the household, and progressively vaguer about people the native rarely meets. An uncle read at two removes, through the parent's house and then the sibling house within it, sits at the edge of what the method claims for itself.
Where the extension to collateral kin was first written down is a question the atlas has not settled. It is recorded as an open question rather than answered with a plausible guess.