Spencer, who also happens to be Kelsey's daughter, was married to James Hesketh for 6 years. James filed Wednesday ... citing irreconcilable differences. The couple has a 6-year-old son, and James says he wants joint physical and legal custody.

Looks like they're trying to avoid a messy court battle -- according to the divorce docs, obtained by TMZ, they are currently in mediation and hope to resolve all property and custody issues there.

Stand down, judge -- and wubba lubba dub dub.