EC: Sponsorer's letter

[Tsar]

Hi everybody,
Feels great to announce that i have got my approval after 1st rejestion which was due to my agent who made typing mistakes in my birthyear which conflicted with my passport age.
Anyway now preparing for my EC. My queries:
1. My father-in-law wud be providing me a notarized sponsorship letter. Question is: does it have to be a notarised letter??
2. He wud be showing his Assets ( Fixed: Land, House + and liquid assets- Bank statements, Saving certificates, LIC, Fixed deposits and Gold). However all above mentioned assets wud be cumulative of my father-in-law, my mother-in-law and my husband and myself.
Question is: Now that its cumulative property can only my father-in-law be my sponsorer ?? or is it that the notarised letter has to be from all of them duly signed??? Not to forget tht my spouse wud be my dependant who also has his share in the above mentioned assets.

Friends kindly help me!