I'm thankful ( ) him for caring for my mother when I wasn't at home.
Which is the proper preposition to write there?
I already know that 'To' must be in the blank.
But also I think 'Of' is fine as well, in that 'Of' means 'relate' between 'thankful' and 'him'.
That is to say, That I am feeling thankful to him is related to him directly.
What I want to be answered is the explaining why 'Of' is not correct semantically.