Isn't that the story of people's lives, they care for someone but that person cares for someone else and have feelings for someone else. Isn't that what caring is about? Even if they love someone else, you had still care for them and want them to be happy even if they don't return the same feeling back. All you can do is just be a friend and love them differently since there are many type of loving someone anyways. Nothing else can be done, atleast not the way you want. Some people change and some people doesn't, same with feelings for human beings. Some things are just beyond your control or not within your reach of power. Going with the flow is just the only thing you may do and even if its not the flow you want or that flow will be disturb. Just the only way some people can care, even if they want to or not. Keep on smiling and be happy with what you got.