Sexual advances from stepfather

I am a First Year student and I have lived with my stepfather for seven years. He loves and supports me very much. He gives me anything I ask for and is even paying my college fees. He is very close to me, especially because my mum always favours his other daughter over me. I think she does this just to please him, but he always seems to love me more. 

Of late, however, he has been making strong and direct passes at me. He even comes to college and spends time with me and many times he kisses and caresses me and tries to get me to sleep with him. I am starting to get attracted to him, but I don’t want any trouble with mum. I have asked him for some time to think about this. He is persistent I think he may even stop paying my school fees and the kindness he has been showing me.