AS partner cheating

Hi, I'm new to this but my partner is recently self-diagnosed AS. He is very intelligent and high-functioning. I just found out that he's being cheating on me in a non-sexual relationship for 3 years with a much, much younger woman  (And, please, before anyone asks, yes, you can cheat without sex or even romance.) Having given this a LOT of thought I think this is more to do with narcissistic personality traits than AS. He's done online tests for various personality disorders and this one fits best to his characteristics, although I appreciate it's all very fluid. Any (helpful) comments or advice gratefully received. 

Parents
  • Autists can be very literal, and as one, both Autist and literal-minded, my brain goes: 'cheating' is a synonym for 'infidelity', which in most usage is short for 'sexual infidelity'. Can one be sexually unfaithful, without sexual activity with a third person? My mind does not accept the concept of a Platonic relationship as 'cheating'. 

Reply
  • Autists can be very literal, and as one, both Autist and literal-minded, my brain goes: 'cheating' is a synonym for 'infidelity', which in most usage is short for 'sexual infidelity'. Can one be sexually unfaithful, without sexual activity with a third person? My mind does not accept the concept of a Platonic relationship as 'cheating'. 

Children