2. The household must be visited by 10 different NPCs—Maid, Repair Technician, Repoman, Baby Sitter, Adoption Service/Child Protection Worker, Pizza Delivery, Butler, Bartender, Bouncer, Pianist, Burglar, Police, Firefighter, Grim Reaper, Newspaper Delivery, Mail Delivery, Science Geek, Magician, Ghost, Tourist, Paparazzi, male/female dancers—who have attained Friend status.
3. The household must have 10 different Best Friends at moving time. There can be overlap with other households’ Best Friends and the NPC requirement can serve double duty here if any are also Best Friends.
OK, I was thinking this was clear, not shore what is confusing,except now your questions are confusing me.
For example, it's time for your first Generation to move, and you pause the game to check relationships. Butler, maid, pizza delivery, repairman and newspaper delivery girl are best friend. There is also a tourist, paparazzi, mixologyst, pianist and bouncer as good friends. Your 1.Generation also has full relationship with future spouse, and that is 6 best friends and 10 befriended NPC's. If heirs little brother have 4 best friends in highschool, than you're good to go (except if one of those friends is newspaper delivery girl your heir already claimed as best friend).
I understood that relationships between household members doesn't count, but anyone from household can count their unique bestfriends to total requirement. I might be wrong with this.
EDIT: And to make shore they visited your household while they are friends, someone with LTR Legendary Host can invite them to the wedding party