This depends on three factors, firstly on whether you are married or not, secondly on what legal arrangement you have and thirdly, with which bank you apply. If you are married, most lenders will require your spouse to be included in both the mortgage and purchase contract. Their reason is that your spouse maybe entitled to stay in the house if you separate, and therefore they want to have a claim on your partner as well. Having a prenuptial agreement according to § 1365 BGB can exempt you from this condition. Finally, there are exceptions and some lenders may not necessarily require you to both be in the purchase contract.
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