Are some people more prone to getting rubella?

Yes: the unimmunized. All humans can get rubella (german measles). If your mother had the disease, you have some protection but only for 6 months. After that, you are on your own. The best defense is immunization which trades a very mild usually inapparent 'infection' for long term protection. Rubella is not innocuous-my sister, for example, has deafness and needed heart surgery in 1945 from rubella in utero.
Yes. Rubella is most devistating to a developing fetus, attacking multiple organs:brain, eyes, hearing& more.Baby can be lost/deaf/blind & severely impaired.If mom had rubella or was vaccinated, the baby is protected during development by maternal antibodies.The antibodies wear off & must be replaced thru vaccinaton or rubella can strike the older kid. Infection when older is relatively mild.