OW moving in to family home

[Shandybass]

I’ve separated from my exh since 7 months. He’s got a new woman and I’ve just been told she’s renting her house out and partially moving in to the family home, as in partially moving back to her Mums and partially at the house. I am guessing it will be mainly with exh.
Anyway I moved out and have 3 dcs. We haven’t started divorce proceedings and I just wanted a heads up as to whether her moving in can have a legal bearing on our joint house? She has no children yet.

It would be unusual for your name to be on the deeds but not on the mortgage. You can check the Land Registry to see if you are named on the deeds www.gov.uk/search-property-information-land-registry

It appears our family property is unregistered. It may be because we built it and it’s not yet been signed off by building control.
I hope this doesn’t make things complicated or worse mean I lose out.

The land would be registered. If you bought the land after 1925 it will be registered.

Doesn't matter whether you then build a house on it etc.

Ah ok not sure that helps Alexa. He owned the land via mortgage before we met and I paid it off to allow him to raise money to build on it.
There was a contract originally but I remember them saying it would be nil and void when we married. I thought that meant equal rights thereon.

You do have equal rights to the family home, it is a joint asset of the marriage.

I am assuming you are in England.