This is Luka Albu, a transfer in at the beginning of this year from Durmstrang. He will be a 6th year Hufflepuff. He is 1/4 Veela, one of the rare males to be born with it, and he is a Romani (Gypsy, though he finds that a derogatory term). Well, half Romani, and he's considered an outcast by them, but that isn't widely known. As in, no one at school knows.
He is also the half-brother to Dorcas Meadowes, though it is not known how that happened, though I am sure it is speculated about, unless Dorcas has said anything about it, because Luka wouldn't go around talking about it. Luka if very social and friendly, and will talk and befriend anyone if they're willing. He is also pansexual. Also to the amusement of Hufflepufff likely, since Luka joined their House he has fixated on his dorm mate Cathal, constantly pursuing him as a love interest. Their scenes are likely very common.
For more info look at his bio. Also, males who change with him have likely seen the scar on him in the shape of a 'G', he wouldn't have shared how he got it or if it means anything. Just smiled and changed the subject.