All you can do is love them, and hang in there----well, if you have a relationship with the other grandparents, you might want to strengthen that relationship if you can..
You don't say how old your grandchildren are, but relationships change as children grow.
It is possible that they sense your anxiety about wanting to be loved etc---and it may make them uncomfortable in a way that they don't understand, and you may try too hard for them. Maybe just letting them be a bit, take their cues re: what to do with/for them; and most of all, do what is good for you so that you can feel good about yourself and let that feeling come from you...
like here today, I know that my own anxiety can interfere with the comfort level of others around me. I hate that but it is so, sometimes just acknowledging my own anxiety is enough to relieve things a bit...a way to say "it's not you...and I do see it..."