Fighting parents...help? ?

ok so my step mom and dad have been getting in many fights lately. the worst one yet was when my step mom came down stairs crying and asking me if i could watch my lil bro (2) because she didnt want him 2 c her like tht and she w/e needed time 2 think and such. so i said sure and just took him in my room and w/e we were playing and he kept saying f***ing because he was there when they were fighting and uk little ppl always copy words. so it took me atleast a 1/2 hr 2 convince him not 2 say it (by saying thts not a nice word, bad word, plz dont say tht...blah blah blah) but i was previously watching my lil sis (8) while they were fighting and i could totally hear them so i just turned the radio up so she couldnt hear. im totally sick of this crap and just want it all 2 stop!! but the worst thing was when my step mom came down stairs my sis asked whats wrong mommy ? and she said me and ur dad just dont get along anymore... i just dont what to do anymore. i really think they r getting a divorce and idk whats gonna happen bcuz my sis already had 2 go thru tht w/ her dad and mom... then me w/ my dad and mom. i just dont know!! what should i do when they fight? should i go take the kids? or should i just stay out of it. this is really making me reconsider going bck 2 my dads cuz i already have enough stress then this. btw i just recently found out my dad is taking drugs (and my mom doesnt know).... so what should i do? i would just not go but then i dont want 2 leave the kids there w/ them when they fight just help?? plz. and SERIOUS answers only plz. sry wasnt sure what section 2 put it in