I'm sorry that you've missed out on an opportunity to connect with these people. Unfortunately, we can't change people or their reactions to things like this.
However, it's possible that the person with ASD in this situation may have more anxiety over social situations or more difficulty communicating with others than you. It could be even possible that he does enjoy your company but does not show it overtly or has trouble taking initiative.
You should ask him directly if he's interested in a friendship and explain how you've been trying to reach out to him for this. If he rejects you, please try not take it personally or feel offended as there's a chance it may not have to do with you. He truly may be busy or may not feel confident or able enough to pursue a friendship.
You should still continue to be friendly and cordial with these people, even though the mom might be a little snobbish. It's just something you may have to accept.
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Given a “tentative” diagnosis as a child as I needed services at school for what was later correctly discovered to be a major anxiety disorder.
This misdiagnosis caused me significant stress, which lessened upon finding out the truth about myself from my current and past long-term therapists - that I am an anxious and highly sensitive person but do not have an autism spectrum disorder.
My diagnoses - social anxiety disorder and obsessive-compulsive disorder.
I’m no longer involved with the ASD world.