If you’ve got double titles when sharing your WordPress posts on Google+, it’s probably due to duplicate OpenGraph tags, which might have been caused by the latest update to Jetpack, which added OpenGraph tags in version 2.0. If you’re already running a plugin that outputs the “og:” tags in your document head, you’ll have to disable one or the other.
For example, to have WordPress SEO by Yoast not output the OpenGraph tags, go to SEO – Social and disable Facebook OpenGraph. If you’d like to disable Jetpack’s OpenGraph support, you’ll have to write some code, preferably in a plugin file:
add_filter( 'jetpack_enable_open_graph', '__return_false' );
Other plugins might be different, but you get the idea.