Although Romeo and J * really show that we must follow our hearts, this is not the theme of the story narrative created by Shakespeare, but a specific point in the plot of that story.
The theme of a work does not refer to a specific point on the plot, but rather the general message that the narrative covers.
In Romeu and J * the theme would be the violence caused by love and the struggle of individuals to get rid of the past of their families. Within these themes, the romance between the two young people and their willingness to follow their hearts do not cover all the complexity and nuances of the work and therefore cannot be considered the theme.
The verb in the sentence is, to follow (his father's footsteps). This verb is used as an infinitive. An infinitive is a word in the verb form that functions as a noun, adjective or adverb. Infinitives are generally introduced by the word "to".
