like I said a relative or his daughter. As for your response
1) Wheres his wife? If DD is 150 his wife could already have died. Just because DD may have decided to take a potion or whatever to live longer doesn't mean his wife did. I think its silly to lthink DD never married, I mean he's all about love and everything.
2)Why would he call he Madame Pomfrey? Out of respect. He calls her Poppy when he's alone with her and Madame Pomfrey around others. I mean, if you worked at the same place as your dad wouldn't you want him to treat you like any other employee and offer you the same respect he gives everyone else.
3)Why would he send her out of the room? Not everyone is in the Order. Maybe she doesn't want to be, maybe HE doesn't want her to be because he doesn't want her hurt. I mean thers lots of people who are loyal to DD but not in the order.
4) WHy would he blush?- Because he was complimented. I still blush when people compliment me.
As for evidence, I'm sure I read something somewhere that gave me an impression that they may be related because I never pull things out of thin air for no reason, but I can't remeber exactly where at the moment. I've got notes in all the margins of my copies so I'm sure I'll find it since I read the whole series through twice a week. (I can't help it, I'm always afriad I've missed something
) I'll get back to you