The Frisky Hawk

Today I read on Digg that Stephen Hawking is getting separated from his second wife Elaine Mason whom he married in 1995. So I was reminded to look up my personal questions about Hawking - his illness, his wives etc.

First of, he has ALS (amyotrophic lateral sclerosis) not MS as I had for some reason assumed. Despite being diagnosed when he was 21 and given a life expectancy of 3 years max, he is right now 64, though he is fully paralyzed. He married when he was only 21. Here he is with his first wife.
One of his earliest symptoms occurred when he lost balance and fell downstairs, hitting his head. Worried of losing his genius, he took the Mensa International test, to verify that his intellectual abilities were intact. Does that seem arrogant?

His marriage with Jane ended in early 1990s when he started having an affair with one of his nurses. Now really, a man in a wheel chair having an affair while there is a healthy woman that is willing to be married to him? Maybe I am being very prejudiced against handicap people, but ... Jane was willing to marry him when she knew he was sick, before he got famous... I don't understand.
Am I so wrong to think this way?
I know once you are famous, you have certain privileges but is this any different to Ana Nicole Smith marrying that 90 year old billionaire?

Another interesting fact I read was that: Elaine Mason's first husband, David Mason, had designed the first version of Hawking's talking computer.