Spoilers below
"Family Life" Have a lewdness level of 0. Refuse to watch any hentai scenes, and make liberal use of an inn or dungeon to avoid the groping scene in the first town. You will go through the game with Sana turning down people like Fief or Kuma (except a few scenes which are canon, but just dont watch them and they dont count). You should only have her sex scores end up with her being groped 3-5 times, they are cannon and cant be avoided. Save scum for the scenes which are time sensitive, like the keys in the orc dungeon, or the mansion where you have to beat the mayor to Sana. If she's avoided sleeping with them and has that lewdness level of 0, you'll get this ending.
"Close Friends" Basically she has sex with Fief, Kuma, Garret or the Mayor. She has one of their kids because she's sleeping with them behind Anon's back. This is the ending if you play the game as intended, with NTR, and "Family Life" is if you play like a person who's avoiding being cucked.