Is it legal for family members to claim a property after 12 years

There are 5 family members - A, B, C, D and E. F is mother of all these family members. After death of F's husband, F divided ancestral properties of her husband between A through F unequally with a mutual understanding and acceptance on an unregistered partition deed in 2009 with signatures of all A-F on unregistered partition deed. 'A' got larger share compared to others. A-E got RTC transfered to each of them separately on their shares of ancestral properties on the same date in 2012. F got her share retained in her husbands name. Many of A-E got loans on their share of ancestral properties on different days and some of sold their share of the properties till now, absolutely with no interference from any one of A-F Unregistered partition deed signed on 2009, But RTC got transferred to A-E individually on 2012. So, A-E individually were in peaceful possession of their share ancestral properties from 2012 till date which completes 12 years in oct'2024. Person A sold one of his share of so divided ancestral property to a person G in 2016. G got RTC transferred in his name and installed borewell and planted few coconut plants in this land. In 2016, G sold this self-acquired property to H. H got RTC transferred in his name, planted few more coconut trees and recently fenced the land also. There is no legal case as on today when i checked with subregistrar office for registration of this property. Now, i want to purchase property from H. 1. Is it legal to for A-F to claim this property which i want to purchase from H 2. Is tranfer of RTC to individual names on 'a same day' in 2012 can be considered as oral legal transfer of property, with undisturbed possession of the properties till date as 12 years is completing, though unregistered partition deed in 2009 is not valid