Conflicted

My moms new BF is a total hunk but is incredibly inappropriate with us including my 14yo sister. He will walk around the house in just his boxers and a semi hard on and my mom won’t say anything. My sister also gets on my nerves because she will allow him to hug her and kiss her on the lips in front of my mom and call her “my little girl”. I think my mom became a pushover after my father left because her new bf is a complete 180. While he hasn’t done anything sexual with my sister he will often cuddle with her when my moms not around and both of them will be wearing little to nothing under the covers. My mom thinks I’m jealous because her Bf is a muscle head and I seem to not be fond of him as much as they are. I just find it weird that my little sister gets to sit on his lap and wiggle around when he only has his briefs on and no shirt. Especially now that she’s starting to fill in bigger undergarments. She’s currently wearing b cups, and the other day my mom sent them alone together to buy new panties. He’s patted my ass before and picked me up off the ground. His strength alone has left me feeling hopeless knowing that he’s essentially the man of the house set to provide for everyone.