@I:
We don't really know about any of the SHs biological families, except Luffy, Robin and Usopp–and even then we still have no idea who birthed Luffy--or Dragon for that matter.
Ahh yea, that's true, that's true, but for some reason, none of the rest of the SH's crew's family history seems to feel as important; either that, or they've already experienced significantly important events that dismisses their family-life as irrelevant (e.g. Brook and Franky). Also, the introduction to Zoro's past seemed so abrupt to me that it made me wonder what got him there in the first place, while the fact that Nami was found by Bellemere during a pirate raid seems like a legitimate start to her story; Zoro's just seemed to have begun, sort of, mid-story, if you know what I mean. O_o
In other words:
Franky ~ He was thrown off of his dad's own pirate ship, end of story. :P The main signifance of his life begins with Tom and Pluton..O_o
Nami ~ She ended up getting caught in a battle between marines and pirates, and was found by Bellemere; it's assumed that her parents are dead, but you never know….But from there, she was raised by Bellemere, and later, became victim to Arlong and his crew.
Chopper ~ Actually, we do know his biological parents, lol. Rudolph's his dad....Naw, just kiddin'. :P We don't really know who his parents are, specifically, but we did see his 'clan' (or whatever it's called O_o) of reindeer...but they're not really anything important, actually; the more important figures of his life are Dr. Hiruluk and Dr. Kureha. ;)
Brook ~ Regarded as unimportant since the main significance of his purpose in life is to reunite with Laboon.
Sanji ~ Like Brook, regarded as unimportant as he was generally introduced in his past as a kitchen boy, and would've had his parents mentioned if they would've contributed anything that really played a big role into finding his dream in the first place.
And yeah, other than that, I think that's what I think of the rest of the Strawhats and their past lives, lol. xD That was kinda hard to express with words, though..:P