Can I ask my brother-in-law to sign a contract when my sister marries far away?

The sister's marriage far away does not affect the brother-in-law's signing of the contract. As long as the brother-in-law is willing and has sufficient legal capacity to enter into the contract, the contract can be entered into. However, before signing a contract, it is necessary to ensure that the content of the contract complies with legal provisions and needs to be negotiated and approved by both parties. If the contract involves sensitive issues such as property distribution and child support, it is recommended to seek professional legal advice.