Sold house with 3 owners. What is my gain?

Sold house with 3 owners. I know $250k for single/$500k for married is tax free. But these owners are not married together. They are Father/mother/Son. Father passed away > 2 yrs ago, so Mom is filing status is Single. Son is married

 

Does Mom get $250k and Son get $500k exclusion.  

on each returns, do I split 50/50 cost/gain from the house? Or do I put the full amount from HUD in each return?