Try the following code to get only the families out that have shared parameter ticked
#Created By Brendan Cassidy
import clr
# Import RevitAPI
clr.AddReference("RevitAPI")
import Autodesk
from Autodesk.Revit.DB import *
output=[]
#May need to change IN[0] to UnwrapElement(IN[0])
for a in IN[0]:
for b in a.Family.Parameters:
if b.Name == "Shared":
if b.Value == 1:
output.append(a)
OUT = output