My mom and dad never talked politics or revealed who they voted for until later in life. My guess would be that Dad was a Republican, and Mom an independent. Both were very kind church-going Presbyterians who did a ton of charity work. Nevertheless, Dad had some "love the sinner, hate the sin" social outlooks.
That changed when a NYC stage actor stayed with them one summer because he was the lead in a play at the Equity theater my sister founded and ran. This guy was gay, and my dad and he eventually became very good friends. Then his friend died of AIDS. It about broke my dad. He became much more liberal in his later years, and my mom became more vocal in that regard as well. They never left the church but they definitely helped drive church policy (which was always pretty progressive in that world).
The idea that a person should be a liberal in their youth and a conservative in their later years is incredibly short-sighted. It may be common, but it's not universal, not by a long shot.