Changing mind after April 15th

[springsteenfan]

I was deciding between University X and University Y and chose X last Thursday (and subsequently told Y I was not coming). 

However, I have recently been made privy to some personal information that would make attending University Y much more desirable (involving sick family members, University Y is in my home state).

That being said, I don't want to alienate the very kind people at University X who helped me through this process/make professional enemies. What do you think I should do? 

[springsteenfan]

University Y could not reinstate my acceptance. Cautionary tale for those who try to fudge the April 15th deadline.