Is it unethical for a lawyer to represent a family friend against the family friend's spouse?

This couple divorced some years ago, and the husband is being represented by a mutual family friend. The couple knew the lawyer in question as they were growing up, and were close friends with the lawyer's parents. Is this an ethical client-lawyer relationship? This is happening in the state of Florida, if it makes a difference.

sounds fine to me

if the lawyer knows private or secret stuff about the person he is not representing, it might be conflict of interest, or something like that.