Speech problems for 7 year old???

I have a son with an articulation problem. He was tested when in pre-k but no problem found since at that age most kids are not able to make certain sounds.Tested again in kinder and found out that in fact he was no able to make sounds according to his age so he was put in speech cles and he is doing great. My questions are: could this be a hereditary condition since it runs in my family?? (little brother couldn't talk until after he was five and had speech cles too) Also is it because I'm not a native english speaker and I know I don't make all the sounds ociated with each word and he pick it up from me??