You would need to create new routes in your plugin like so
helpers.setupPageRoute('/:groupslug/:userslug', middlewares, function (req, res, next) {
// todo: get uid of user using req.params.userslug
// todo: check if user is member of req.params.groupslug
// todo: render account template with all data
});
You can take a look at the core user routes on how to do most of this stuff.