KanjiJLPT N1
Join

join, get together, unite, collective

Mnemonic

Butler Alfred stands before the gate dividing two neighboring estates. His master has ordered him to join them into a single domain. Alfred unbars the gate, swings it wide open, and the two properties merge forever—one grand household under his meticulous care.
Additional thoughts
Picture Alfred physically removing the gate that separated two lands, symbolizing deliberate unification. The gate is the barrier; the butler is the agent who eliminates it, consolidating everything into one.
Quick recall
Butler Alfred opens the gate between two estates to join them into one.

Details

The keyword for 併 is join. This kanji conveys the idea of merging, combining, or bringing things together side by side into one unified whole. It often implies the act of annexing or consolidating separate entities, such as territories, organizations, or concepts, so that they function as a single unit. The sense is one of deliberate unification rather than a casual coming together.
On'yomi
へい
Kun'yomi
あわ.せる