It is possible. You should be having a field in your XSD schema for the username. Bind the username to a hidden field in your form.
In the designer, in form initialize event,
write the code: if hiddenfield.rawValue == "person A"
subform1.presence = "hidden";
if hiddenfield.rawValue == "person B"
{
subform2.presence = "hidden";
subform1.presence = "visible" }
In your process, when your moving from one step to other step, update the uname accordingly and the form will respond according to the username.
Regards,
Chaitany