Ring that was a gift

What is the name of your state? Texas

we were given a ring from my wife's grandmother.
her father wants the ring, he is pressuring to sue for the ring.

he states that we extorted the ring from her grandmother because of her old age and mental status.

if he were sue could he win ? or would he have to get medical proof that the grandmother is mentally incomp?

Thanks in advance
Kiote

The only thing I have to offer is, that the Father would have to prove a connection with ring to him, and that Grandma didn't give it to you as a Gift .