Looking at German Rail's website, it states that children 14 and below traveling with adults are free. But for Rail passes all children above 6 have to buy (up to 12 are 50% off). Above 12 have to buy a youth pass.
Is that true? Why is that? The same for all eurail passes?
Yes, it is true. Children under 14 ride for free on German Rail (including German Rail services abroad) when in the company of a fare paying adult (in theory, this is limited to parents and grandparents, but never checked). This is no promotion and applies to standard fare tickets as well. Eurail passes are a different matter.