If you have a good relationship with your boss, then it shouldn't be a problem.  Just ask to meet with him/her privately and then let them know what's happening with your family and that unfortunately you need to quit.  Once they've digested that information, it should be okay to ask if they would mind being a reference for you when you're looking for a job in your new location. 

You will probably need to put your resignation in writing as well.  But if you've discussed it in person first, it won't be a big deal.  Most bosses I've ever dealt with are appreciative of honesty and in being given as much notice as possible - as they'll usually have to replace you.

Best of luck with your move!

I would say just come clean and tell the truth reason. If you have a good relation already with your employer, the best way is just give them a real reason. I'm sure they would appreciate that. Specially with your reasonable reason of moving 3hrs away. It just too much for you for sure to travel extra 6hrs every day to go and back from work. It just not make sense at all. So, again, I'm sure your boss/employer would understand that....and give you good reference.

Good on you bent one.I would just tell them you need to move for personal reasons and then thank them for assisting in the state of your mental health and you will send the bill for your shrink!!!! roflmfao.............just kidding I would then thank them for helping you to gain more experience in your current line of work and generally kiss ass.......well you know what I mean LOL Just be as consice and to the point as possible whilst thanking them for your employment opportunity with their company.Good luck luv from Twisted Sistah mwah

i think the best way is to tell them you have to go, you are really sorry as you love the job but you have to move so many hours away from *inset name here* eg. mum and dad.
i think its the best way to let them know instead of packing up and leaving them with little knotice and you can, by saying what i have said, get a really good refference,

i hope the move goes well for you, lots of luv & luck,

xox channy