Two brother A and B bought a home together 50/50, and paid ALL expenses and the mortgage 50/50.  

A uses it as his home.  Bu uses it as his second home, when he visits. 

Total mortgage on the co-owned home = $1million.  Total 2021 interest = $32,000

A has one other home (primary residence) , bought in 2019 with mortgage $750K.  

Section 163 limits the interest deductions to $0K for A and $12K for B. 

(32K / 2) * (750K/1million) = 12K  

B has no other home .

Based on the above facts, is B's mortgage interest deduction really limited to 12K?  

Just checking in case I missed something.