An Acts7brother is someone who does his neighbor wrong.
24 And seeing one of them suffer wrong, he defended him, and avenged him that was oppressed, and smote the Egyptian:
25 For he supposed his brethren would have understood how that God by his hand would deliver them: but they understood not.
26 And the next day he shewed himself unto them as they strove, and would have set them at one again, saying, Sirs, ye are brethren; why do ye wrong one to another?
27 But he that did his neighbour wrong thrust him away, saying, Who made thee a ruler and a judge over us?
28 Wilt thou kill me, as thou diddest the Egyptian yesterday?
29 Then fled Moses at this saying, and was a stranger in the land of Madian, where he begat two sons.— KJV, Acts 7
Notice that it was he that did his neighbour wrong that accused Moses.
For all the law is fulfilled in one word, even in this; Thou shalt love thy neighbour as thyself. — KJV, Galatians 5:14
Or maybe it was a believer. Because also believers can do wrong to each other:
(Galatians 5:15 [KJV]) But if ye bite and devour one another, take heed that ye be not consumed one of another.
Either way it is a fellowship issue when someone does evil to you. So we should do as Moses did  and depart from the person.
Gods advice regarding Acts7brothers
We should do like Moses and flee from him (Acts 7:29).