These are legitimate requests if you are in latter stage due diligence. If you are at this stage, you should be at a point where you are pretty positive that the firm and its people will be accretive if they do decide to participate in your company.

It's a bit dicey if you've gone through preliminary chats and into DD while not being 100% about the people at the firm yet. Definitely don't just jump off the DD train since it can be hard to get that rolling again. However, do get a beer or lunch with them ASAP and really try to get a hold of whether you trust them and want them as partners.