When all stats are tied (like max SPECIAL), intelligence is inherited.

This post (Apples_Brother) has the breakdown for every combination of tied stats and what stat wins the tie and is inherited. If a parent has multiple stats tied for highest, the game has a built-in algorithm for determining which stat it considers to be the highest for that dweller. The primary stat of the parent is whatever their highest stat is at the time of conception (outfits not included). Children inherit the primary stat from either parent at a 50/50 chance. With common children for example this will be the stat that starts at 3 while the others have 2 or 1. It does not change their total SPECIAL, just which is highest with the points they have. Children will always have a 'primary' stat, one that just starts off higher than any others. There are only two methods of influencing SPECIAL, one being the chance at getting rare/legendary children with high stat parents (see 5.4), and the other being highest stat inheritance. Q: Can I control SPECIALs in the children I breed?Ī: Yes, but you have limited control.

Fallout shelter breeding wiki