Bench mates, school mates, college mates and family mates are from the same life-time. However, soul-mates are companions from many life-times.
When one has contact with others from many life-times then they are called 'soul mates'... Krishna and Arjuna were soul mates...Rukmini and Krishna were soul mates. Their companionship comes from many, many life-times.
Husband and wife are life-mates. Soul mates come into your life with a common soul-purpose.
At soul levels, there are many generic families which come down with a common purpose. Many big soul-families exist separately for music, meditation, enlightenment, sports etc.
Any two people.. if they have a common category of interest.. then they become soul-mates in that particular field. They have friendship and oneness between them. For example, music brings oneness and friendship between two musicians.