What instrument family does the organ belong to?

Answer 1

A classical wind organ, with pipes (PEDDLE DRIVEN OR ELECTRONICALLY DRIVEN AIR SUPPLY) belongs to the woodwind and keyboard group. A modern electronic organ or synthesizer is an electronic keyboard instrument.

The pipe organ is commonly known as the King of Instruments. It was never designed nor intended to duplicate any known orchestral instrument, so it is in a category all by itself, and not a member of any "family" of other instruments. See the related link below:

Answer 2

It belongs to the strings group, like the piano.