This topic was not one that I had trouble with. My Mom and her brother were very willing to share stories and info. My Pop generally said that he didn't really know anything about the family, but every now and then I'd share a new find and he would reminisce with helpful details. My 1st cousins, mostly 10-15 years older than me, were also willing to share stories.
Of course, some of the memories were a bit out of whack and needed to be verified, but overall fairly reliable.
Make a list of questions you want answered.
Have a photo or other document available to get things started with reluctant relatives.
Be polite and patient.
Take good notes!
Check online for suggestions on genealogy interviews.