Is it safe to put my rabbits together?

unless you neuter or spay one of them you should never put a male and a female together because they WILL have sex and you WILL end up with babies. The phrase "hump like rabbits" is very true, ser you get mend if you want to put them together you get at least one fixed because even for a second with her he could get her pregnant and you do not want to deal with all of those babies =P