Why would an insurance company need information on someone who is not listed on a home loan?

So my boyfriend recently bought his first home and I agreed to move in with him. However, his home insurance agent is asking for him to provide her with all of my information (social security number, driver’s license number)

Mortgage Protection Insurance for my UK home. I need it, but which insurance company shall I choose?

I have been offerred mortgage payment protection insurance by my mortgage lender, but it seems a bit expensive. I think my job is OK, but I do worry as there have been a few people made redundant recently