A better question would be ... Even IF he is interested in you, WHY WOULD YOU WANT THAT DRAMA?!?
Even if he "does the right thing" and gets a divorce, before you two enter a relationship - you are going to do nothing but bring strife to the entire family.
I actually know someone this happened to. A friend of a former boyfriend cheated on her husband with her father-in-law. The aftermath was so much more devastating than an affair with someone not involved in the family. As one's marriage is crumbling you can't turn to your family for support because their marriage is crumbling as well. And the biggest loser in this whole mess were the kids of the younger couple.
If you are asking is it possible that he have innapropriate feelings for you .. Then .. The answer is yes, of course .. It's 'possible'. Anything is 'possible'.
However .. I would suggest you be very careful on how you choose to judge his 'affections' .. Could his affections be typical of any family member that loves his family members .. Or is there something unusual and innappropriate going on that is making you feel uncomfortable?
Whether or not he is 'happy' is irrelevant. If he IS feeling inappropriately towards you .. then YOU need to react in an appropriate manner by not encouraging his 'attentions' .. and 'snip' that in the bud.
The easiest way to tell you how is remember when your Husband first met you and then chased you? If your FIL is acting the same way or close enough , guess what? Older guys are always interested in younger girls but most know its a forbidden apple when a marriage is involved, boys will be boys at any age and will try in hopes for catching the impossible.
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