Suggest Medication For Cold And Bronchiolitis

I have a 6 months old baby boy and seems to get a cold all the time, since December to now march, he has suffered from 4 colds and also had bronchiolitis , he gets congested and suffers with a snotty nose which means he doesn t settle well through the nights, he has also never slept through the night due to these colds reoccurring. I use saline nose drops, a vaporiser and a humidifier to help him be more comfortable through the night but still nothing helps. My mother-in-law suffers with her heart, has a very low to nothing of a immune system and has M.E. so I am also concerned that maybe her problems have been passed down to her grandson?