I can see where the concern is. At my store we had an ETL who's nephew was my flow TL. He was a sh** stirrer. When I first arrived there he would complain how the ETL-Replen discriminated against him and didn't let him lead. Kissed my butt basically. Well I told him that flow is his team, so lead them. Have an idea? Do it! Then when my Replen quit and we got a new Replen he did the same to me. He told the new Replen and HR that I discriminate against him and don't let him lead. By the way, I only worked with him twice a week. Then when I left, my Replen told me that now he's doing the same to him with the new Log.
I've tried coaching and CA's, HR just threw them out (friends with his aunt). He was accused of sexual harassment 3 times by 3 different TMs while I was there, nothing happened. All three TMs quit and each TM didn't know each other or worked at Target at the same time. He was obviously dating a subordinate (who was married) yet nothing happened. This guy was protected.
I did make our monthly status meetings uncomfortable. I always had him as my bottom performer and when my STL would ask for documentation I gave her my copies, which HR conveniently couldn't find. When I knew I was leaving, or at least didn't care at this point, I made his nights hard. For my other TLs I set them up for success. I had cages out, I bowled, I'd push an entire section before the truck was finished, I'd take care of beverages, almost anything to give them a head start. Hell I even jumped on the truck some nights so we could get out on the floor faster. When it was his night I sat in the office or helped backroom. Towards the end I just watched movies the entire night or sat in the break room watching TV. Also I would recognize the other TLs on how well they were doing at huddles. I gave him a reason to feel discriminated against in the end.
Why did he get away with stuff? Because TMs wouldn't come together and speak out against him. They were intimidated by his aunt and HR. My suggestion, speak up. Work with HR if you see something wrong. Collaborate with other TMs / TLs who feel the same way. Remember the hotline! It's there for a reason, but make sure not to call unless it's a last resort.
Also, don't worry until you see something wrong. Some relatives can work together well without showing favoritism. I know if my brother was a TL I'd treat him exactly the same as other TLs. No favoritism on my part because at work we are a team and each have to pull our own weight.