Whilst I agree that from what you have said it does sound perfectly reasonable that you keep everything, I would like to put across my mother's experience from the other side.
She left an abusive relationship with my step father after falling in love with an older man who she met as she was hos carer. You are probably all judging her right now - I certainly was horrified especially ad he was still married and living with his wife. He had picks disease, a bit like Alzheimer's and his wife had stayed with him purely for appearances, she had a boyfriend she went to for weekends.
Anyhow, the shit hit the fan, the wife found out and moved the husband into a shelters accomodatuin and divorced him. She fought tooth and nail against my mother having contact with him, until she realised it was to her advantage. Then she let mum move in with him and basically be his sole carer for free for the rest of his life.
Mum constantly made it clear she wasn't after his money, signing agreements not to marry him and giving financial control to his daughters.
5 years later, with us having basically become his new family as his wife and daughters hated him, had done even before he got ill, he died.
Obviously mum was not in any will which was still the one from his married days so didn't count. She never asked for a penny, but they made her feel like a vulture even though she had been thee for him for years and was by his side as he died.
They kicked her out of the house a week after the funeral and tried to sell things in the house she had actually bought. They were absolutely vile about everything, even down to deliberately giving him a funeral that was the oposite of his choice.
Not saying open and brother are like this, but want it known there are always two sides. Maybe the girlfriend did love him. Maybe she deserves to help plan the funeral, and enough money for a holiday to recover from the stress of caring for a dying man and then losing her home. I think she would be happy with just some respect from you and your brother and less suspiciousness at her motives.
I also think you and your brother are dutybound to provide enough for Yuri mother to retire and have her own home. It sounds like she really deserves and needs it.