Attention willy nilly

What I just wrote to Ambre, has me pondering something that is bothering me.  While H does not seem to care about me or our marriage or the state of the family or responsibility or his own integrity, he has been very attentive to one of our granddaughters, Age 11.  She is quite beautiful and innocent.  H follows her around like a lovesick adolescent, with eyes sparkling and a big dreamy grin on his face.  He often puts his body in her close presence like he is "feeling her vibe", like he did when he and I were 15 years old and now I see how I was overtaken by his attentiveness and close encounters when I was an innocent girl myself.  Like he was emitting testosterone pheromones and turning me on.  I thought it was love and "chemistry".  I am concerned because my H does not act like head of household financially, grandfather to young grandchildren, responsible father to my sons, loving husband to me but rather like a boyfriend to the one granddaughter.  While our other, younger granddaughter, the sister, gets sarcasm and no attention from him.  

Writing this is making it clearer to me.  Sometimes I think the problem is me in that I am too judgemental and I back off trying to be fair and not be critical or jealous.  I feel uneasy about letting them alone together.  Not that I think something sexual will happen but that ... it is wierd. Granddaughter is liking the attention, the secret jokes, the touching heads and laughing and that she is getting more attention than her sister. He is flirting with her and it feels very bad to me...and to our other granddaughter. It feels unhealthy to me and I can't exactly craft the words right to say. "You are not her boyfriend!" seems like a fight starter.  "Act like a mature grown up that we can admire instead of a clown." will fall on deaf ears. I try to put myself in his shoes and how I would want my spouse to talk to me if I was doing something inappropriate.  But I know that if someone were to tell me I was doing some of these things I would totally take it to heart and really change just by the mention of my inappropriate action.  H seems to have a "kill the messenger" response to anything I say and tells me I am crazy and wrong.

What are the words I can say to H?  If you have ADD or ADHD, let me know what words could I say that would not cause a reaction of attack on me for bringing it up and insinuating something horrible?  I don't know if H is able to hear the words and understand that he is being inappropriate.  His family culture is touchy feely and often cross the lines of what is appropriate. How do I approach this?  Any of you spouses have a similar situation of being at once uneasy with the ADDer and also wondering about your own judgment? Anyone have to lay down some rules about acceptable behavior and what you will put up with and what is not acceptable to you?