Doubts on Parents Visiting Visa

Hi,
I'm planing for my parents visa. Could someone please help me below doubts

I'm in Tier - General Visa, and sponsoring all expenses & Accommodation everything my self to my parents.

1) Do they need to go for General Visitor or Family Visitor ( I heard only ILR visa person can sponsor Family visit visa) ?
2) How to submit my parents 2 applications same time with same case worker?
3) For both my parents do i need to provide each two supporting documents or each one document enough (Like Bank statement / Pay slip etc)?
4) My own Brother & sister in India, what evidence documents do i need to submit related to Indian family relationship for my parents (to prove they are going back)? Any way i'm submitting property & land documents but still ?

Please some one help me for the above things.
Thanks