Hi Seema!
If you have a sharing computer, your family members can all join in the forum with separate accounts (if you like) so that you will each have a different identity here in the forum.
If you are all going to be using the same computer for Little Reader, it will need to be installed in one Windows User Account (in your computer) and you will only need one license key for it, since it is only one PC unit.
I hope that answers your questions!
Cheers,
Lappy