Affinity

noun

1. A natural attraction or feeling of kinship to a person or thing.
2. A family relationship through marriage of a relative (e.g. sister-in-law), as opposed to consanguinity (e.g. sister).
3. A kinsman or kinswoman of a such relationship; one who is affinal.
4. The fact of and manner in which something is related to another.
5. Any romantic relationship.