Is it permissible to belong to a tribe other than the one to which a person is related by lineage, and what is the ruling on disobeying the elders of the family in this matter?

What your elders did by affiliating your lineage to a tribe you do not belong to is forbidden by Islamic law. Your duty is to correct the lineage to your true father, as affiliating oneself to other than one's father is one of the gravest sins. We advise you to handle the matter with wisdom so that family ties are not severed.