Hello I(27F) have a 10 month old daughter. She's been going through a happy screeching phase and we have been trying to work on soft tones. She is starting to understand. She also does fuss sometimes if she makes a tumble now that she cruises on furniture. Usually if we don't make a sad expression or negative reaction she's perfectly happy after a brief few seconds. However, my nephew ( 10M) just spent the night after a full day of birthday festivities with us. He has mocked her screeching even louder and has even tried to get her to screech. He also will tease her with toys and put them out of reach and twice I caught him taking her bottle away in the car. I told him at least 3 times to not mock her like that and she copies so she will drone on. When she fussed after a minor fall yesterday, he did it again and she cried more than the few seconds she usually would. I tried once more to reason and say "I'm sorry if the noise bothers you, I know baby crying is frustrating but can you please leave the room or put on headphones next time. She will stop crying after about 10 seconds once she knows she's safe" . Today she face planted on the tile because her dumb mom, me, didn't realize the floor was so wet after cleaning her highchair. She started screaming much more than normal so I could tell she really was hurt and then my nephew chimed in with an even louder scream. He was in another room when this happened. I yelled " , STOP" from the other room. My husband (29M) and also his biological uncle said I was way out of line. AITA?