Double rex is also referred to as patchwork (since the hair usually falls out and comes back in in patches). Hairless will usually just have light fuzz on the face. It comes down to what mom and dad were. Two rex parents = double rex. Two hairless or hairless recessive parents = hairless. From what I've seen of your rats, I'd say they're hairless.
Yeah, if it was the case that both parents were standard coated then they both carried the hairless gene as a recessive and probably produced about 1/4 hairless in the litter. Rex is dominant and double rex is two co-dominant rex genes, so both would have to exhibit rex to actually carry the gene.
its highly possible i believe they were imbread the guy just keeps all his togeather and actually had rain and thunder togeather before i got them they have since been seperated and were monitoring rain for sighns of pregnancy sofar we have had luck with no sighns and its been almost 3 weeks