The problem is how do you define an off-topic link. There are far to many tangential relationships between things.
Aunt Tilly's Flowers gracing the table of Uncle Elmer's restaurant
Uncle Elmer's contributions to the neighborhood little league stadium
Grandpa Chester's windshield repair service fixing glass broken by baseballs at the little league stadium
Grandma Elsie's Car Lot, providing the vehicles used by Grandpa Chester's business, and also leasing Aunt Tilly delivery vans for her cut flowers.
Are these really "off-topic"? How can an algo tell?