Sharing iCloud + features with a family member living elsewhere

As long as they all have their accounts set to the same country. Apple does mention possibly not being able to access certain features if you are not in your home country, so if the other family member lives abroad but is using your country it may still work but possibly not for some things.

Apple Media Services Terms and Conditions - Legal - Apple Media Services - Apple

- A. ”Our Services are available for your use in your country of residence (“Home Country”). By creating an account for use of the Services in a particular country or territory you are specifying it as your Home Country.

- J. “Certain Services and Content available to you in your Home Country may not be available to you when traveling outside of your Home Country."

Apart from some minor systems requirements for iCloud services (see here) Apple has not been restrictive about use of a Family Sharing group in their support documents such as Share iCloud+ with your family.

The only requirement I have seen is that all members must have their own Apple Accounts and these accounts must be in the same country.