I am honestly shocked by a lot of these responses. These are adult men who have never lived in this house, not children. No wonder so many second subsequent relationships fail when one person thinks their adult kids with no ties to the house have more right to say what goes on in said house than an actual paying occupant!!!
His house. His kids. His rules
This is an appalling attitude. He may own the house but it is also OP’s home where she pays 50% of the bills! She has every right to expect some common courtesy and respect from her partner and his adult offspring.
Imagine any other scenario where the “my house my rules” thing would be played out, it would be called controlling and out of line.
Anyone who has this attitude has no place being in a relationship! If her DP wants a healthy relationship then he needs to accept there will be some personal boundaries of hers that need to be respected.
She is not banning them from the house or saying they can’t come over, but expected adult men to send a quick courtesy text or ring the doorbell is perfectly reasonable.
Before I lived with my STBH, my children would have free reign access to my bedroom and lie on my bed to watch tv etc.
However, now DP & I live together and it is also his bedroom they know to knock or ask if it is ok. My DP likes a bit of privacy to get changed or take a shower and I respect that. My kids aren’t his children and he is perfectly entitled to put a few personal boundaries in place for his own comfort.
Similarly, my SDs both have keys to our house but either quickly call on their way over or ring the doorbell / loudly announce themselves when they enter. I had an incident a few months ago where the eldest had quietly let herself in and I was wandering around my home naked as I thought I was alone... only to be met with my embarrassed and shocked 16yo SD standing on the landing upstairs. It was bloody awful and could have been avoided had she just sent a text or rang the doorbell before unlocking the door.
OP I would find it hard to have several adult men who I am not related to having free reign and access to my home at all times. You are not unreasonable to expect a quick heads up so you know whether they’re there or not.