A Muslim guy proposed to me. My mother agrees to the proposal as the guy is religious and have equal standing with me. We are both lawyers. He is religious and comes from a good Muslim family.
My father is already deceased. The relatives of my father are neutral on the subject.They said it is up to me and my mother and my wali.
My mother's brother (Abass) and my grandmother, (Johara) and my wali (my brother Abdul) do not agree to the proposal on the ground that he comes from a different tribe. and that it is a disgrace to our family's pride.
My uncle and grandmother told my mother that they will disown her and that they would not forgive her if she allows me to marry the guy. My uncle even said that he will have my brother Abdul leave his wife (who is our cousin, daughter of Abbas), should the marriage take place.
Based on their argument the same is against the teaching of Islam. But my mom is at a loss especially if she allows me to marry even if her own mother forbids it. Is she committing a sin if she disobeyed her mother.
And is the reason behind my wali's objection valid? Can his authority over me, pass to my other younger brother, since his objection is purely unISlamic?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

If this young man is as you mentioned that he is religious and has a good moral conduct, then he should not be refused as a husband because the criteria for choosing a spouse should be religion and good moral conduct as we clarified in Fataawa 88093 and 82298.

Indeed, those who refuse to accept him because he is from a different tribe or for being from a different family status are undoubtedly wrong. Therefore, you should try to convince those who refuse to accept this marriage. If they are convinced, then praise be to Allaah, otherwise, their objection should not be taken into account. Your mother is not obliged to obey her mother (your grandmother) because her objection is not for a sound purpose. For more benefit on the limits of obedience to parents, please refer to Fatwa 84942.

Moreover, if your older brother refuses to marry you off, then your younger brother may marry you off if he is pubescent. Besides, your maternal uncle should not threaten to divorce his daughter from your brother if this marriage takes place.

Nonetheless, if you think that it is better to avoid this marriage with this young man in order to preserve the ties of kinship with your relatives, and you are safe from being harmed if you do not marry him, then it is permissible to apologize to him and Allaah may facilitate a good spouse for each one of you.

Allaah Knows best.