Who can "gift" you a down payment, and how are those gift down payment funds verified? (S5 E16)

Realtor John V. Pinto and Abel Fregoso, Senior Loan Officer at
Homebridge Financial Services, talk about the ins & outs of
having a blood relative assisting in your purchase of a home.
 They can give a "gift" of some, and in some cases, all, of
the down payment you need.  Find out what kind of paperwork
the lender will want to see.