Cyrus's 15 wives
Wikisimpsons - The Simpsons Wiki
Appearing in Simpson Christmas Stories these women are Cyrus Simpsons's Native Tahitian wives.
When Abe comments that he must have a lot of sex, Cyrus dryly replies that "I said wives, not girlfriends." To which the girls completly agree.
None of them appear to be that old, seeming to be in their 20's or possibly early thirties.