I'd model people as one entity (table), relationships as another entity, and relationship types as a third entity. The relationsip entity would link two people (one weak like a chile, the other strong like a mother in the modeling sense) and describe their relationship type.
If you need to support multiple langages (English, Spanish, French, etc) you'll want to use Unicode and will need to support some kind of equivalence grouping within the relationship types so your code can easily tell that child, niņo, and enfant were equivalent relationship types.
-PatP