My 2 year old twins have strep throat and have been taking anitbiotics since monday. one has a barky sounding cough. is this still strep?

No, most are viruses: The fact that strep is found does not mean that strep was positive of symptoms. Most cold-type illnesses such as that with your twins' cough are viral. Probably initial symptoms were viral-related. Swab was done in strep was found. There is a latin expression "post hoc ergo propter hoc": meaning: since strep was found, it is presumed to be the cause of symptoms. Not necessarily so.

Cough and strep: This needs to be reported and discussed with the treating physician as it may be a complication of the strep or a new condition. Re-evaluation is in order if the condition is getting worse or changing.