Re: mujhe choti wali pasand hai!!
He may just be posting for fun. He did not even come up to that larkiyo ki pictures on facebook thread to justify himself and opened another thread where he insisted that he liked younger girls when he visited to see the elder ones. He must be one smart munda on earth 
Coming back to the topic, I again insist that parents don’t allow other daughters to meet the potential rishta families (unless the age different between the daughters is very small) so that such things of picking and choosing girls don’t happen. Parents have their own opinions. Its a different argument that youngers ones should not be left unmarried because of elder ones. But this picking and choosing girl by the visitors seem like a buyer is choosing vegetables from a shop, bari wali nahi choti wali de do.
Still a guy/ his family likes the younger one, they can conver this to the parents afterwards and see their response. Things can proceed if parents are ok with it.