Those who pay huge sums of extra money ($11,000 or more) for First Class deserve all the peace, quiet and extra space they've paid so much money for. To some First Class clientele, having people from Economy hanging around visiting friends in the First Class cabin cheapens the over all experience for them. Personally, were I setting policy on this, I'd err on the side and wishes of the folks paying the mega bucks rather than those folks from Economy who don't feel they're being much of a bother. Whether they are or not is not their call to make.

The crew has the final say but above all, I think discretion is the key element here. Were I seated in First Class (I often have been on international flights) I wouldn't personally be put off by your occasional quick and quiet visit to check in on your relative.