I too am alone family wise apart from an older sister but due entirely to most of my family dying before I was 24.Yes it has been hard(no immediate baby sitters etc)BUT I do have the one advantage.I will not see my parents dwindle into old age and infirmity.No worrying about them being able to take care of themselves in their own home.No worrying that they are getting inadequate care while in a retirement/nursing home.
I have been spared all that.
However my children have only had one set of grandparents who because they were in Wales my children did/do not see them as often as I wished.They have missed out of the passing on of family history,culture and wisdom(what teenager listens to their parents) which I feel is their true heritage.However I do have strong memories of my own early family life and this is perhaps what I should remember and try to pass to my own children.
AS for close personal friends I too don't have many of those.I reckon that the friends are the ones we can manage to keep connected to.The problem is with some friends that you have to do all the running if they move away or you move.Not many of my friends bothered after I or they were out of sight.Yes I have tried to keep in contact but eventually it becomes one sided.So I reckon that if you have kept connected to a mere handful of friends you are doing well.
I think I'm just too self reliant for friends myself.

I learned to stand on my own two feet at 13 when my father died and I just have broad shoulders when it comes right down to it.If I want advice I talk to my elder sister sometimes who frankly is probably my closest friend.There is nothing I can't discuss with her.She too has been on her own so to speak for a very long time.She left home at 17 after a blazing row with my mother but managed to patch things up eventually.My father wasn't about to lose his bright smart daughter that easily.
Personally I think it is best to have as few regrets as possible or you end up losing it and wallowing in misery.What's past is past and time to look to the future.After all you can't undo the past but you can weave the future.