Proximity and physical closeness can do a lot with our emotions. I would be leery of his living with you all all this time and the closeness, too "automatic". If Jack is not initiating interest (being as close to you as you are to him) then I would not do anything in this situation, would maybe move out on my own or have him move out or something? I would explore the world without Jack as it has gotten complicated with him these several times and that is all you have known.

The age may seem like it does not make a difference but it does. What you want at your age and what he wants cannot be similar because he literally lacks the experience. Your backgrounds, etc. cannot have been the same, there is nothing there to help hold you together. My husband is 7 years older than I am, we are in out 60's and even now the age thing is making differences; it is quite likely that my husband will be much less able to do things in the next 10 years than I will be and that will cut into my life. Another person has to be a partner or lives drift apart but being a partner with someone with a different age or background (never mind both) causes difficulties one doesn't necessarily foresee.

Sexually wanting another (wanting to be kissing Jack when you're kissing another) is not a great, enduring reason for wanting to be with another; sexual attraction is there "first" to bring people together and you then get to know the person as themselves and see if you want to stay together. But one can be sexually attracted rather easily/often; that is a "no-brainer" whereas true relationships take more than sex.

I guess you could ask him if he wants to try a friendship with benefits relationship but that would probably get your hurt as your friend says. I would see if I could spend more time away from Jack and "move on" with someone closer to my background and age?