For any finite set $S$ and every partition $S_1, \dots, S_n$ of $S$, let $P(S_1, \dots, S_n)$ be the family consisting of all possible unions of $S_1, \dots, S_n$. Clearly, $P(S_1, \dots, S_n)$ is a union-closed family and all elements of $S$ are abundant (present in at least half the sets of $P(S_1, \dots, S_n)$).
Do all union-closed families such that all elements are abundant come from partitions?