Language Barrier

What is the word one uses to describe a parent that loses a child?

When children lose their parents they are orphans.
When a wife loses her husband she's a widow.
When a husband loses his wife he's a widower.
When you lose a significant other you never married,they become an ex--an annex of the "you" from the past.

*This thought brought to you after I watched Season 1: Disc 3 of Six Feet Under.

And what of those who've lost siblings? Most importantly a twin, an identical one for that matter? There should be words for that...for all of those.

In Eskimo there are 33 words for snow, in English we have but one. In India, there are specific, different relationship names for every kind of person who marries into your family--different for men and women. In India one refers in English to male cousins as "cousin brothers" and female cousins as "cousin sisters". Thus illustrating value of relation and significance therein by gender and lack of familial distance.

What cultures have words for all of those kinds of loss?