Have an impact. It will not affect your doctoral thesis, but it may affect your development after doctoral graduation, because after doctoral graduation, if you are engaged in scientific research, you must apply for funds. Especially good schools require you to leave without promotion, and the conditions for promotion have requirements for projects and funds. To apply for a fund or project within three years, it is generally what the doctor who applied for you did. If your brother applied for funds and projects with your doctor's things, you can't take a doctor after graduation. In other words, it is difficult to make something new before you have time to review the fund after your Ph.D. graduation.