are the instruments in the string family old?

How do you define "old?"

from what time were they in existence or which century?

2500 B.C.

http://en.wikipedia.org/wiki/String_instrument#History

To determine if the instruments in the string family are old, you can consider the following factors:

1. Historical Background: The string family of instruments, including the violin, viola, cello, and double bass, have been around for several centuries. The design and construction of these instruments have evolved over time, with the oldest surviving instruments dating back to the 16th century.

2. Age of Specific Instruments: The age of a string instrument can be determined by examining its craftsmanship, materials used, and any historical records associated with it. Instruments with a long history are often prized for their sound and historical significance. However, not all string instruments are old, as newer ones continue to be made to this day.

3. Condition and Patina: Older string instruments often show signs of wear and aging, which can be seen through the instrument's surface condition, such as cracks, repairs, and patina on the varnish. It is important to note that not all old instruments have a well-preserved condition, as factors such as maintenance, repairs, and past usage can affect their appearance.

4. Documentation and Expertise: Seeking the opinion of instrument experts, such as luthiers or appraisers, can provide valuable insights into the age and authenticity of a string instrument. These professionals often assess the craftsmanship, materials, historical context, and other factors to determine the age of an instrument.

In conclusion, while the string family of instruments has a long history, not all instruments in the family are necessarily old. Evaluating factors such as historical background, age of specific instruments, condition, and seeking professional expertise can help determine the age of a particular string instrument.