So my mom had a dream that a gray owl was flying on top of her and she suddenly grabbed him and threw him and my brother wrapped him with a towel but she didnt hear the owl at all
The owl represents something all knowing, ever present. Grey could mean wisdom, like wisdom from old age and therefore could represent authority. So the grey owl could represent a wise, all knowing, ever present authority like God or parent/grandparent. The reaction from your mother indicates that she feels shame, anger, guilt towards herself and she may feel anger towards God or parents/grandparents.
Your mother may have suffered deep emotional wounding like from sexual abuse as child, she feels it was her fault, she feels shame, guilt and she feels angry toward possibly her parents or a parent or grandparent/s and possibly toward God. She doesn't want anyone to know what happened.
Your brother is younger than you. He is about the age your mother was, when she was abused. The fact that she wrapped him in a towel indicates she wants to protect him and comfort him. Your little brother is in essence her (your mother) as a child, she is doing to your brother (wrapping him in a towel) what she wanted done to her; to receive a feeling of love and security.
Hearing is the distal sense. So the fact that she didn't hear the owl represents that she feels free from the past, like thinking; "its all in the past now, i don't think about it anymore, the negative emotions from the abuse (anger, sadness, shame) they don't bother me anymore, i am ok now...". Your mother thinks she has healed and she might have, but there is still a little girl inside her who has a broken heart and carries heavy burdens of sadness, guilt, shame and anger.
I know what i wrote sounds pretty far out but this is what i feel and think dream indicates.