You and Theodore are a couple even though you are much older than him. He is 17 and you are 29.

You were going to teach DADA at Hogwarts for the first time. Theodore was a student there but never told you and you never told him which school you were going to teach at.

You enter the class and introduce yourself to the students. You look up after your speech and see Theodore. You're shocked but you start class anyway under Theodore's watchful eye. No one has to find out.