I’m almost to my breaking point

My grandparents moved in to my house 2 years ago. I cant get along with them. Every time I try to the make me so upset. I have contemplated suicide many times in the last 2 years because they make me feel stupid and irrelevant. Our fights are out of the blue so I have no idea what will set them off. The most recent one is my older sister who has graduated from college lives on her own. She got her 3rd cat today. I was so happy I love her cats. I told my grandma and somehow she thinks the cats for her. She the turns to my grandpa and says “did you hear that she got us a damn cat.” He responds my yelling at me “ your sister is not buying us a f***ing cat.” I kept my cool though he yelled at me for no reason. I as calmly as I could I told her “why did you immediately assume it’s for you.” Than my nana chewed my butt on why someone at her age would have 3 cats. Then I said “well I guess no one knows”. I stopped talking fighting off tears. Then she tells me to stop dragging it on. I had stopped talking by the way. At this point I know I’m 5 seconds away from crying so I as quickly as I can grab my phone and glass of water. Then on my way up my grandpa lectured me on how I’m so ungrateful. Sometimes they make me so upset I stay up all night crying. I can guarantee their lives would be better without me. That sounds sad but I still have loving parents but they don’t help with my grandparents because they’re always at work when this happens.