in need of advice

we are renting a house from my boyfriends mom. his brother lives in the home as well. keep in mind that we do have a baby. well his brother is always smoking weed outside and when he comes in the whole house sticks REALLY BAD. I'm disgusted!. the was 2 times he smoked in the home. he has been talked to about it. but my boyfriend doesn't want to put him out or the mom either. Idk what to do. it's been going on for 3 months now . WHAT DO I DO ????:(

HELP ME PLEASE ??