“I pray for them all daily.....But especially for myself that I continue to have faith in the message of+ Jesus Christ.”
I envy your siblings for they have you to pray for them.  However, I believe if one was Catholic, they are Catholic the rest of their lives whether they know it or not.  We have not lost Catholic faith, just having problem with corrupt clergies.  We will figure out a way to worship God as a community without the corrupt clergies.
Meanwhile, 'Above all, love one another deeply, because love covers over a multitude of sins.'.      (1 Peter 4:9)
Love God always, love unites and you are always united with God in your love!