Is it safe for my 2 male cats to play with my 2 pregnant cats??

I have 4 cats altogether, 2 boys and 2 girls. My eldest male has been fixed but my youngest male hasn't and neither have my 2 girls. My girls came in heat at the end of December and low and behold, my male kitty did what's natural to him and had them both so to say. They are house cats so they're always aru d each other. The girls are about 4 weeks pregnant now and they are starting to get quite round. Im just worried that when the boys are playing with the girls that they might harm the babies. The boys can be quite rough and I don't want the kittens to b harmed. I've never had to deal with pregnant cats before as my mum always had our cats neutered when I was growing up. So any advice would be really greatful.

Hi and welcome 

First of all, please get both the un-neutered male and the two females fixed. The two females can be spayed now with no harm to them and it will be safer and better for them than if they need to deliver the kittens.  

As for separating them, you will of course want to do so if you think the males are really being too rough/hurting them, yes, but the better time to have kept them separated would have been when the females were in heat.  

Please familiarize yourself with this article about why it is a good idea to spy and neuter your pets.  http://www.thecatsite.com/a/spay-and-neuter-your-cats