Wand choosing the wizard

[marinafrants]

No: HPFGUIDX 39052

The way I look at it, the wand does choose the wizard, but that
doesn't mean the choice is either unique or permanent.  A wizard can
"grow out" of his or her first wand and be chosen by a new one.  For
example, we know Charlie Weasley must've gotten a new wand at some
point, since Ron ended up with his old one.  This raises the question
of why Charlie didn't just keep his own first wand and buy a new one
for Ron.  My guess is, Charlie had grown out of his wand, so it wasn't
working quite right for him anymore.  When you work with dragons, you
can't take chances with an ill-suited wand, so he had to get a new one
that worked perfectly.  And since there weren't enough funds for two
wands, Ron got stuck with the hand-me-down.

Also, just because you haven't been chosen by a particular wand
doesn't mean you can't use it -- it just won't work quite as well. 
We've seen numerous wizards use someone else's wand: Sirius used Ron's
and Snape's; Crouch Sr. used Harry's; Ollivander used Harry's,
Cedric's, Krum's and Fleur's during the Weighing of the Wands; and
Wormtail used Voldemort's to kill Cedric.