In a separation or divorce, a stepmother's rights often hang in limbo.

Sandra Bullock is the stepmother of Jesse James' three kids (Chandler, Jesse Jr. and Sunny). Now that he has cheated and she has reportedly moved out, what will happen to the kids now?

Bullock has publicly battled James' ex -- porn star Janine Lindemulder -- for custody of 6-year-old Sunny. Will Bullock be able to see Sunny and the other kids if she splits with Jesse? To find out, we talked to attorney Steven Mindel.

"Sandra Bullock is not a biological parent, so in California, her legal visitation with the kids will be dependent on what Jesse James and the biological mom say it should be," Mindel says. "She can still see the kids if one of the parents is present -- but if she wants to take the kids for five hours every Saturday independently, both biological parents will have to sign off on that. It's not going to happen without the consent of both parents."

Continues Mindel, "The biological mom could say, 'I absolutely do not want this woman alone with my kids.' And the biological mother's wishes will take precedence. My guess is that Sandra is going to have limited access with these children unless she's with Jesse -- and I can imagine she's probably not really happy with him right now."

Mindel offers another scenario: "Now, she could also get visitation with the biological mom present," he says. "I know she's been fighting the adult-film actress for custody of their youngest, but war makes strange bedfellows. Your enemy yesterday could be your best friend today."

He says Lindemulder may want to use Sandra Bullock as her star witness in future court proceedings. "Sandra could say, 'I was the one who was primarily taking care of the 6-year-old,'" he says. "Sandra wouldn't be testifying against Jesse necessarily, but the court could infer that Jesse is incompetent to take care of the children on his own. Sandra then might work with the mother to get her time with the child. In these types of situations, the whole game can get topsy-turvy real quick."

Mindel says that Jesse James' own custody situation could change. "His rights were pretty dependent on the fact that he was in a stable marriage with Bullock," he explains. "Now that he's not stable, all of the custody could be up in the air. It's up to the judge's discretion -- but if a judge wants to look into it, there are grounds to do so. Jesse is already coming out, making a public apology -- how stable is he to take care of the children now?"

We hope that everyone involved does what's best for the kids. They are innocent victims in this big mess.