Are you already a good candidate for a great residency program? Do you already have good letters of recommendation? If so, and you have a good reason for taking the year off, I don't think it will hurt your chances very much. If you plan on applying to a super competitive specialty like Derm or ENT, I would recommend you have some research or something academic lined up during your year off early on to talk about during interviews. (After interview season is over, you can do as you please.)
I took a year off and got into a top Internal Med program with no problem. Interestingly, no one ever asked during interview season what I was doing during my year off. I did explain why I took the year off in my Personal Statement, but I still expected someone to ask, "So, what are you doing now?" But, it never came up.
Most places/people are understanding of family issues.