Delphin Slade was clearly a very handsome, charismatic man. Otherwise, he wouldn't have been competing for the attention of not one, but two women at the same time. A wealthy, successful corporate lawyer, he would've been a real catch for any woman. That both Alida and Grace were so keen to be with him suggests that, despite their superficial differences, they look for similar things in a man.

Unfortunately for Alida, she doesn't recognize this fact until it's too late. She never would've guessed in a million years that Grace and Delphin were lovers and that their brief, illicit tryst resulted in the birth of Grace's daughter Barbara. She was always so sure that her cruel little ruse, played all those years ago in the middle of a Roman fever outbreak, had worked like a charm. That it didn't shows us that Alida never really knew either her husband or her friend. Among other things, this would appear to suggest that Delphin, like Grace, was a bit of a dark horse, able to conceal a more complex personality beneath his thoroughly conventional exterior.

Delphin Slade was the husband of the now-widowed Alida Slade.  We know from the conversation between Alida Slade and Grace Ansley that he must have been a very attractive man, since both of the women were interested in him, when they were younger.  We also know that he was a charming and successful man. Alida Slade has found out that since his death, her social life has almost disappeared and has now realized that Delphin, as a corporate lawyer, was the one who people wanted to associate with.

When later we find out Grace and Delphin had had a triste while he was engaged to Alida, we know that Delphin was not necessarily the most faithful of men.  Yet, the fact that he follwed through with the engagement to Alida without ever betraying Grace shows that he had some honor.  When we later learn that Babs is actually his daughter by Grace (from that one-time meeting at the Colleseum), we can gather a bit more about his personality from Alida's description of Babs--lively, vivacious, charming, daring. 

What we can deduce from Delphin's personality tells us quite a bit about the female characters.  Alida underestimated her husband as she underestimated Grace.  She unintentionally set the two up, and when they secretly met, there were fireworks.  But neither Grace nor Delphin pushed for Delphin to break off his engagement, and they each carried their secret for a long time--Delphin to his grave, and Grace until Alida pushes the issue.  Delphin shows us how intense feminine jealousy, such as Alida's, can be,  and how some women, like Grace, sometimes fail to play by the rules but will always maintain a sense of propriety.