I've been working my FIL's 'Lavelle' family for 3 years, since they lived with us for 6 months 3 years ago. (that's a lonnng story, LOL)
One thing that was difficult was that all I had to go on was the stories my FIL 'knew' from his father. When I found new info, he would say, 'oh yeah, that's what my brother said Dad told him' ...supposedly he and his brother were told different stories about their grandfather.
So, how do you 'ask' the inlaws about their lines?