Starting with 'Do Gaz Zameen Ke Neeche (1972)', which actually isn't a bad movie at all, the Ramsay brothers didn't come from cinema royalty, as quite a few actors/directors/etc in Bollywood in particular tend to, but they actually got into film after their father (F. U. Ramsay) opened a couple of electronics stores. DGZKN was their first (and possibly only) notable movie that really helped them get into the swing of budget horror.
Thanks to that movie, they were able to finance quite a few low budget horror flicks, a vast majority of them in the 80s. India wasn't, and still isn't known for their horror. This is perfectly understandable, when you remind yourself that a lot of Bollywood cinema does have musical numbers. It's almost impossible to make a terrifying picture in the midst of that element, and a lot of times it does take away from the very little horror that is available there in a big way.
The Ramsay brothers essentially ruled the roost in Bollywood horror in their hay day, because they were tapping into something nobody else really was. There was an odd film here or there, but really, the vast majority of even the more horrific Indian films tend to leaned towards noir. There were, of course, plenty of copycats to follow, but the Ramsays were the first. They also tended to do a lot of 'screen-stripping', the art of watching one movie, writing down your favorite bits, and throwing it into a new script with a different title and enough of your own flare to technically call it a different movie.
The introduction of the action boom in the early 90s saw their schlocky horror fare taking more of a backseat, as audiences simply lost interest in reincarnated demon-werewolf babies produced from the seeds of vengeance, promiscuous behavior, and murderous ancestor husbands. Their last true film they made in the genre was a Bollywood answer to Nightmare on Elm Street, 'Mahakaal'...which, like most of their movies, took your basic popular Hollywood film and applied a cultural wash. But, after that, they did the 'Zee Horror Show', which as a popcorn muncher...can be pretty fun. Afterwards, at least on the small screen, there have been countless different horror anthology series who I'm not afraid to say were and are heavily inspired by the Ramsays.