Yes, I think I read somewhere that 10% of children are not biologically their fathers'.. although this might not have been because their mother's husband was infertile/impotent, could have just been a good old fashioned affair.
I think I also read that in the old days when newborns were all put in a larger nursery together at the hospital mix-ups also got made, also found later in life due to medical treatment, when they matched neither father nor mother! But don't think that happens any more.