What is the expiation for a father's false oath taken to ratify a marriage contract due to the inability to provide the required documents, and does this entail sin for the questioner and his fiancée?

If your father and the two witnesses swore falsely to establish a right that could not be attained otherwise, then there is no blame upon them, nor upon you, nor upon your fiancée, because lying in this case is permissible. However, it is preferable to use allusions (ta‘areed). But if they swore falsely without necessity, then they are sinful and must repent. According to the majority of scholars, there is no expiation due upon them. However, according to the Shafi‘is and one narration from the Hanbalis, expiation for breaking an oath (kaffarat al-yameen) is obligatory.