As the title; I'm not seeing anything against it, I just know a lot of class abilities are limited to the class they're from normally. As a Druid 2/Wizard 1, could a character share say... mage armor with their animal companion? Or cure light wounds on their familiar?
At the druid’s option, she may have any spell (but not any spell-like ability) she casts upon herself also affect her animal companion.
At the master’s option, he may have any spell (but not any spell-like ability) he casts on himself also affect his familiar.
Any spell means any spell, including those from other classes. Yes, you can do this.