Ancestral property - Partition Suit filed by daughter (Christians)

I seek your assistance in clarifying a legal matter involving my father, who is the defendant in a suit for partition filed by my aunt. The suit was initiated after her marriage, which took place nearly 60 years ago. We are Christians, and my grandfather had four children: two daughters and two sons. One of the sons passed away unmarried around 40 years ago. Both daughters were married, and my grandfather gifted them land and gold at the time of their marriages. The remaining son, my father, took care of my grandparents throughout their lives. Notably, one of my aunts is not interested in this suit and has chosen not to participate, but the elder sister has filed the suit. The properties in question were inherited from my great-grandfather and were managed by my grandfather, who held the Pattadar passbook. In 2007, my grandfather executed and registered a gift deed transferring all the property to my father. My grandfather passed away in 2011, by which time he no longer owned any property, as everything had been legally gifted to my father. Despite these facts, my aunt, with malicious intent, has filed this suit with false allegations, claiming a 1/3 share of the property. However, my father had the properties mutated in his name back in 2007 and has been in peaceful possession and enjoyment of them ever since. It is also worth mentioning that my grandfather performed my aunt’s marriage grandly and provided her with gold and land at the time. I kindly request your clarification on the validity of this suit, especially in light of the fact that the properties inherited by my grandfather are now being claimed as ancestral. Can these properties be treated as self-acquired under Christian law? Thank you for your time and assistance.