Claim on Joint properties

Hi. My Grandfather has purchased some properties on my fathers name! He has 3 sons & no daughters. 1.The income generated from businesses of my grandfather of amount nearly 5 Crores as whole taken by only elder son since my grandfather has expired ( expired on 2000 july) . 2. My grandfather has helped his second son for going to US & settle there 35 years before. And he has given an amount of ₹10 lakhs by selling the flat that was on my fathers name in Tirupathi in 2010 by my grandmother & not even a single rupee was given to us. 3. My grandfather has directly purchased 10 Acres from the seller on my dad's name - when 2 acres were purchased my dad was minor - when 1 Acre seperatley on 1991 & 7.5 Acres on 1993 while purchasing these both properties my father is major. ( Only these 2 properties (10 Acres) which are on my fathers name from Joint family properties are more valuble than other properties). Now I'm trying to sort all things and settle once for all between all three : A. I'm telling he has taken total of our share in income so he has to pay atleast 70℅ of that to agree and divide. If he agrees we are also ready to give share in the properties which are registered on my fathers name. B. Now they both 1st son & 2nd son came into agreement without our notice and 2nd one is also getting share in Incomes from my grandfather businesses. C. Now they are not willing to pay us & wants to go to court for settlement & claim all the properties including properties on my fathers name without paying us single rupee. My concern here is that if they go to court & wants to claim the properties which are registered on my fathers name by showing that it's a joint family property - Are they going to get share on properties or can we claim those properties that we bought them with our own Income? And here one more doubt that 2 Acres is purchased when my father is minor so how to deal with that property? Are they going to get share on whole 10 Acres? Or will they get in 2 Acres? Or can we claim entire 10 Acres? Or some part of 10 Acres.?