"I'm looking forward to more families benefiting greatly from this measure." I don't see any issue with the sentence. It means "I'm looking forward to an outcome whee more families benefit greatly from this measure." "more families benefiting ..." is a gerund-based noun phrase describing a situation or outcome, so it can be used as a subject, object, or a complement of a sentence, or an object of a preposition as in this example. Gerund phrases come in two kinds, with or without a subject. When it has a subject, it can be nearly as versatile as a general noun clause, as we see in this example. Other similar gerund phrase examples: (with no subject of its own - it defaults to the subject of the enclosing clause) - I love swimming (a gerund used as an object of a verb) - I love going fishing on the weekend. (with its own subject) - Your [or You] standing there doesn't bother me at all = Even if you stand there, it doesn't bother me at all. - It was a time of everyone fighting everyone else = It was a time when everyone fought everyone else.

It is grammatically correct but sounds a little odd to me, I would just say "I'm looking forward to more families benefiting from this measure" and leave out the greatly. I don't know why exactly, it just sounds more natural in this case.