Is it normal i want to stay in touch with my co-worker

I am at an internship and there's this man there i've come to get along really well with even though he's older and I really like him. We're also both on the autism spectrum.
I want to stay in touch because i've never met someone so similar to myself who understands and experiences things the same as me.
He shares a lot of personal things with me so he's either a very open person or he likes and trusts me I guess.
He's apologized before for talking about his problems but I didnt mind because I could relate to so much that it made me feel less lonely. Then he revealed that he's on the autism spectrum.
He'd always come to sit with me at lunch and we'd talk for so long that eventually only we were still sitting in there.
I've hoped he will mention wanting to stay in touch, go for coffee outside work or something, but he doesn't...
And soon we won't see each other anymore. I have a month left at the internship and he's going to job interviews reguarly so he'll probably find something and leave anytime.
I am worried I will seem silly or weird (due to the age difference) if I want to stay in touch and that it will come off creepy. .-.
I want to imply how I feel so that he suggests staying in touch instead of me... How can I do this? What subject to bring up that can lead to this? I think i'd have to be pretty obvious, without being pushy, because he's kinda awkward and seems like a careful type of person who doesn't want to embarrass himself too much or make anyone feel uncomfortable.
For clarification I am 26 and he is 41. Is that too much?
I have mentioned to my family about him before and they strongly disapprove of us just being friends at work even which makes me upset. I dont understand the problem?