I don't think Parsley.js provides this functionality out of the box. Instead, you can write it custom by registering an onchange event listener like so:
$('input#others').change(function() {
if (this.checked) {
$('#otherinput').attr('disabled', 'false');
} else {
$('#otherinput').attr('disabled', 'true');
}
});
Note: this assumes lowercase ID names (i.e. 'otherinput' instead of 'Otherinput').
I haven't tested, but something like this should work in theory.