The old people which you are referring to must have mistaken the blood type with the resus factor + and - . In cases when a mother is negative and the father is positive the child can inherit the positive resus factor which may lead to problems during pregnancy.
In your case, as the people before me said, there is nothing to worry about.
if you're blood related yes the children can have birth defects. if you just have the same blood type...don't worry.
Okay, both of my parents have the same blood type and I turn out fine. So, don't worry about it.