step dad keeps making sexually suggestive comments

my step dad keeps making weird ass comments at my mom and it’s making me so fucking uncomfortable. i can tell she’s uncomfortable too, even tho she tries to play it off. she kept trying to change the subject and he kept circling back to it. eventually, she rejected his advances several times and he still continued. idk what to do.

is there even anything i can do? he says it openly in front of me (20F) and his kids (14F and two 13M)—sometimes with my mom around, other times even when she’s not around. it’s fucking disgusting. i don’t think his kids catches on cus they don’t really speak or understand our native language.