A middle aged couple decided to try one last time

A middle-aged couple, with two beautiful daughters,
decided to try one last time for the son they always wanted.

Soon, the wife became pregnant, and, nine months later, delivered a baby boy.
The joyful father rushed to the nursery to see his new son, but was horrified to find an incredibly-ugly baby.

He went to his wife and said, “I cannot possibly be the father of that hideous child.
Look at the two beautiful daughters I fathered.

When his wife blushed, he became suspicious, and demanded,
“Have you been fooling around on me?”

His wife confessed, “Not this time.”