How to locate elements relatively

how to get element’s parent/child/sbling.

there is a way to get parent in this issue How to locate to parent node?

if we know elment’s xpath, we can construct xpath to get.

but if we just know the webElement class, how to a get relative elments?

for example, there is a tableView, with many tableCell. ech tableCell have a label and textField. the label is different, we can locate the label by name, but how to locate its sbling, the testField.