So I'm strongly looking into Graduate Schools in Europe to obtain a master's degree in my field. This would be a huge life change of course and would require me to leave home for two years. I might be able to go home to the States for the holidays but I'm not sure since it is costly. My biggest hesitation is because I'm an only child and I feel bad leaving my mother. She doesn't get along with my dad and they are both getting older, she will be 60 this year.
I guess I feel like it is my responsibility to look after them since no one else will. I know that it is important not to let things hold me back in life but I have a lot of lingering feelings since I'm the only one. My friends are supportive but none of them are only children so I would love to get some advice from other only children who have left their families for extended periods.
The longest I have been away without seeing my family was this summer when I did a study abroad in Germany for 2 months. I felt really guilty before and after the trip but I loved it while I was there.
Sixty is not that old. I'm sure they appreciate you being around, but are they really that unable to take care of themselves? Feels somewhat unlikely to me... They'll only get older, so if you ever want to head out, there's really no better time than right now. (It'll also give them a chance to learn not to depend on you too much, while this is still a lesson they can benefit from.) Much though you might love other people, you really need to live your own life, and not let potential worries about others hold you back. Go do some travelling so that twenty years from now - when they might really need your support - you won't resent them for having prevented you from travelling at all.
Pretty much everything Sander said.
Obviously we don't know the circumstances around your mother and her state of health but as an example mine turned 60 last year and despite generally being a homebody, her wanderlust kicked in only a few years ago and I wouldn't dream of presuming she couldn't take care of herself.
By the summer trip you mentioned it also sounds like you are an immensely close family, but is it just you feeling unnecessarily guilty or do your parents actually pressure you to stay in touch/stay nearby?
Your parents had (and are still having) their life.
Now it's your turn.