Heh, my DD has heaps of aunties and uncles - not all of them are my brothers and sisters though. In addition to my brother and sister, DH's sister and brother in law she also has my best mate from school, a couple of my own aunts are aunty as well, plus a number of step-aunties and uncles.

We're auntie and uncle to DH's godkids as well as his niece and nephew.

To us it's a respect thing as well as a way of showing a level of closeness and affection - DH's family think the world of my daughter even though DH isn't her father and I love them all the more for it