Dear Eric: My older sister is a recent widow. Her husband was unfaithful to her several times, but she chose to stay together. One of his indiscretions was allegedly with a childhood friend of mine, with whom I’ve had sporadic contact over the years. The friend recently contacted me, out of the blue, to have dinner together. Neither my sister nor I know if anything actually happened, and her husband always denied it. My sister is now asking me to ask my friend the details of the affair.