Naughty Girls on the Loose (1976)

Custer Firkeshaw, the owner of a girlie magazine, stands to inherit a fortune...IF he can get married and have a baby within a year. When he (and his relatives) find out from his doctor that he only has 13 more...uh, attempts-at-procreating left in him, the relatives set out to ensure that he uses them all up, so that they can inherit the property.