互い, たがい
May take 'no', See お互い
each other, one another
結婚は2人が互いを理解し合えばすばらしいものとなりうる。
を
Particle
1. indicates direct object of action
2. indicates subject of causative expression
3. indicates an area traversed
4. indicates time (period) over which action takes place
5. indicates point of departure or separation of action