Sometimes a persons demons or difuculties are such that makes it from their perspective, much more dificult to open up to or talk to about with a family member. That doesn't mean as a family member you shouldn't ask if you suspect something,but that you need to realize they may feel they need to protect themselves or a spouse or a child or another familial relationship by NOT telling a family member. In realizing this suggest or find a friend or professional outside of that persons familial circle who can/will listen and can help.

Alternatively as a friend or an acquaintance of someone, YOU may be even more important and have an opportunity to help someone to open up and start a healing process that others much closer to that person can not do. Keeping this in mind, be vigilant in being your fellow man's "brother or sister father or mother" by doing what their family is often unable to do.
Take time as you move through the daily adventures or boredoms of life to ask a person how they are doing. You will have to ask twice in most cases at the least. The first time people will think you are simply making conversation or pleasantries.. You HAVE to follow up with something like, " No. Seriously, How are you really doing? What is going on with you? " etc. Give them a chance to let it out. Then be their family.

A friend is a powerful thing.