A kindred spirit is someone with whom you share common interests, similar likes and dislikes, loves and hates. It might be somebody who has a similar sense of humour to yours, or who has had similar life experiences, or who has a similar philosophy of life. Basically you will have least one and probably several things in common, which bring you together: it is people who are 'on the same wavelength' as you, who are 'like-minded' or 'of the same mind'. This 'could' be a 'boyfriend' or 'girlfriend' but not necessarily. People sometimes get together, or get married because they discover that they are kindred spirits, but sadly this is not always the case. It is probably more common to use the expression 'kindred spirit' in the context of very good, close friends, rather than those necessarily in some kind of relationship. Or it's also quite common to describe people who don't even know each other, (perhaps even separated by space and time) as kindred spirits, just because of their similarities.