What's happening
A Full Moon occurs when the Moon stands at 180° from the Sun — directly opposite from Earth's point of view. The lunar face is fully lit because the Sun and Moon are on opposite sides of the zodiac. The sign reported for the Moon is the sign it occupies at the exact opposition. A Full Moon in Cancer means the Moon is in Cancer while the Sun is in Capricorn.
The Moon is in its own sign of rulership at a Cancer Full Moon, which the tradition treats as a dignified and particularly vivid placement — the Moon expressing its nature without having to work against the sign it is in.
The tradition
Cancer is ruled by the Moon. A Full Moon in Cancer is therefore the annual peak of lunar themes in the most lunar sign: home, feeling, memory, lineage, caregiving, the protected interior. The opposition with the Capricorn Sun adds the counterweight: structure, public role, the visible life, the ladder.
The classical reading of this opposition is the tension between where you live and where you perform. The Capricorn Sun wants the work to show; the Cancer Moon wants to be allowed to come home at the end of the day. When the two are in opposition, the question of whether the outer life still has a liveable inner one tends to surface whether you invited it or not.
How to work with it
Let the feelings come up honestly. This is not a phase for sentiment to be managed into acceptable shape; it is a phase for feelings to be told the truth and given their weight. Call the family member. Say the thing about the relationship you have been avoiding because it is too much. Let yourself be held, or notice that you are not being held and name that.
This is also useful weather for the work-home boundary — noticing where the ladder has been costing the kitchen, and making the adjustment that lets both be real.
The shadow is using Cancer's depth to stay inside a grievance rather than move through one. The Full Moon's gift is visibility; the gift is wasted if what becomes visible is just re-rehearsed.
The simple rule
Ask what home is asking for, and whether the outer life is honoring the answer. The Full Moon in Cancer rewards the honest inventory of belonging.