I think friends 'go' only if you let them. You stop answering calls or making contact. Not all family is there for you. At the risk of sounding like Dom Toretto, I feel you can make your own family. It's not a blood thing. Some people can be closer to you than blood relatives.
Sam and Robert are the hitch-hikers on the road.
--Necronomicon incantation (The Evil Dead)