A family member is living with me and has syphiliscan we get the disease from them using our toilet?

It is possible. If the infected person has a "chancre" which is an open lesion teeming with the syphillis organism, and touches the surface of the toilet with that lesion, then one could get direct contact of their body (genitals) on that innoculum and contract syphillis. It would be very unlikely but it is possible. Don't want to scare your and this is very much out of the ordinary but possible. Be careful!