there is a question about neighbors

hi I'm Jada

I live in a house with 5 floors and an old elderly grandmother lives
above my apartment on the first floor.I take care of her and her son
wants to give the apartment to us for it! But they have a brother who
also has a share who lives in Poland. He says that after the death of my
neighbor, he gives it to us for what we helped her, tell me after what
time the will comes into force