He likes to lord it over his younger brother.
lord it over
idiomTo behave as if one is in control of; to make a display of having an advantage over or superiority to.
Origin
disputed originFrom lord over.
She got a promotion and now she tries to lord it over everyone in the office.
Despite his lack of actual authority, he continued to lord it over his colleagues, creating a tense and resentful atmosphere in the department.