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As married couples you may choose to share things with your partner like joint savings acount and also contribute for some projects together like building project but having a joint Bitcoin wallet should not be encouraged. Aside running away with the funds, if your partner carelessly exposes the private keys or seed phrase, you're screwed. If both of you want to invest in Bitcoin, do it separately, not everything are meant to be shared.
The phrase not everything are meant to be shared can be contradictory sometimes. Bitcoin can be a shared investment, if it is properly arranged. Imagine a couple is using a hardware wallet and the device can be stored in a vault where two individuals can have one part of the piece to accessing the vault. By now we must have watched movies where the keys in accessing a secured file is separated only one of the keys cannot open it. That is the same case i am explaining here. Sharing a Bitcoin investment account is possible if it is properly planned.