Repeating patterns
Often family members will have either some of the same patterns as others in the family, or patterns involving the same planets -- just in a different arrangement. We might think of this as a form of astrological genetics.
Having a full moon, or Sun opposed Moon, pattern may or may not be significant. It probably is, but it doesn't have to be. Each of us seems to respond to some patterns or elements in our chart while ignoring others. As a general rule, which can be greatly modified by other chart factors, the Sun-Moon opposition points to people who seek and learn from relationships, who are aware of where others are at and are coming from. That's not to say that they are great a making friends, they could be antagonistic, but they will be involved in relationships of one sort or another as a means of learning about life. If the opposition pattern also involves other planets, then that will modify what I indicated. Dave