You have not committed any mistake or Sin. It was only Baba’s wish. As I used to say (moreover it is my hard experience). All such relations are set even before we take birth on earth. To honour the words of parents is indeed a good thing. If his parents were against his marriage, not he, He must have come to your parents to hold your hands at his own, but he could not show that amount of courage. It is not so easy to forget such relations, but if you committed your life towards your husband and his family, You will be able to maintain your peace of mind and bring harmony in both the families. (Your parents and in laws).
May Sai bless him too with whatsoever best is in his destiny and you a happy married life!
om sri sai ram!