No, that's not necessarily so. Patti may well have had problems (no eggs, blocked fallopian tubes, etc). But it's also possible her body may have rejected George's sperm cells. In some couples it seems that although both are fertile, there is a response (akin to an allergic response) of the woman to the man's sperm, preventing fertilization.
However, Patti's marriage to Eric Clapton was also childless. This doesn't prove that it was Patti that had the problem - but it seems more likely than not.
