(1) Lineal relatives are reciprocally obliged, on request, to supply information on their income and their assets, to the extent that this is necessary to establish a maintenance claim or a maintenance obligation. On the amount of the income, on request, supporting documents, in particular certificates from the employer, are to be submitted. Sections 260 and 261 are to be applied accordingly.
(2) Before the end of a two-year period, information may be demanded again only if it is satisfactorily demonstrated that the person with a duty to give information later acquired a substantially higher income or further assets.