The fear of missing out? That's just one of the many addictive strings that Facebook tugs to manipulate you. The things that happen on Facebook don't matter. If something is important then it is far better to discover it outside of Facebook. In the end, nothing is that important.
There are other ways of keeping up with old friends and relatives. Listen to gossip from other friends and family. Keep in contact with them using email, telephone and post. If you don't maintain some link then they should be resigned to the past - until some event occurs to trigger a re-established connection.