I don't know what kind of relationship your WH and FIL have - my guess is strained or nearly non-existant - but at the VERY least, FIL might be able to penetrate WH's thoughts having "been there, done that" and now seeing it 40 years later from the other side.
"Do you want your precious baby girl to grow up hating YOU as much as you hated ME because I left?"
Totally Agree...
this could be a huge trigger of emotions for your WH. It would a moment where your WH would feel like he was looking into a mirror image of himself in years to come!
