Never had any bites, but I've offered family/close relation roles for my characters before. However, I refuse to just post a recruitment and allow the first person who shows interest to have the role. Mostly it's people I trust.

Namely with one of my technophobic characters, I've offered two roles to a couple people before. Admittedly the reason I hold back on just doing a recruit post is I have a basic idea of what the character is about. One of the relatives ICly is to have known my character quite well for the past 80 years, I'm not going to just lightly offer such a role.

Both times I've offered I got turned down, but it wasn't a big failure since it was a bonus, not anything critical I needed to have.

And to answer the second question: Definately have a set of ideas for the characters' behaviors.