I was wondering where the à came from. Ressembler is one of those verbs that require à plus an indirect object: http://french.about.com/od/grammar/a/preposition_a_3.htm
It's a little more like this: Verbs with the preposition "à" require indirect object pronouns: me, the, lui, nous, vows, leur. If not using a pronoun the order is SVàO. Elle ressemble à ma tante. With a pronoun, SOV without à. "à" isn't in the sentence anymore, but is understood because of the ind. obj. pronouns. Elle lui ressemble. (Lui replaces il AND elle) A similar verb would be téléphoner à quelq'un. And you're right about the reflexive. "Ils se ressemblent"