Sale of Joint Tenant with right of Survivorship -

My sister and I were put on my mother's house as JTWROS.  We sold the home, but my mom is still living.  We all received 1099-S.  How to we report the portion we received?  This was not our main home, nor a second home to my sister and I.  Also, is the cost basis the FMV upon date of sale?  Is this amount then divided by 3?