Dad died before divorce was final. Can we (my brother and I) contest the beneficiary of his pension?

I'm guessing that the timing is unfortunate, and probably can't be fixed.

Usually, if a divorce was in process, and some sort of finalization agreement was signed (even if the divorce itself wasn't finalized), then you can petition the probate court, using the signed divorce settlement agreement as evidence and have the court order the beneficiary changed post-mortem. Speak with a reputable probate and estates attorney in your area for more specific advice. Good Luck!

I agree with Mr. Lauser. The estate should be able to have the property settlement agreement enforced.