I don’t know. 3 nights is half their time, so they are 50/50 basically and every place they live should be a home, not just somewhere they’re staying.
I agree with this. They obviously live with their mum 4 days a week, so they don’t really have one clearly defined ‘main’ home. They didn’t ask for their parents to split up and to have to live their lives between two different houses. If both parents said “well, they’re only here for 3 or 4 days a week, so they can make do” (for all we know, their mum might have a new partner with a toddler, just the same as OP’s situation) where does that leave them? Whatever their father does or doesn’t do, they shouldn’t have to suffer just to teach him a lesson.
We don't know the ins and out. Its not clear who has paid what so far, what the difference in income is, if he actually draw disposable income from the rental, whether there was any talk of marriage before the inheritance came about.
There are many factors to take into considerstion before reaching the conclusion that he is a cocklodger and we only have very few so far.
I wondered this too. He might well be royally taking advantage, but equally his own property might just be breaking even (or costing him extra for the time being) – hence no money available right now to pay for converting the loft. He could be planning on maintaining it as it is until the mortgage is paid off and then for it to be a family asset that actually starts bringing in extra money, IF the relationship survives. If it doesn’t, he’s protecting himself as we see women advised to do so often on here. It’s not like OP is paying rent or mortgage for their house, so maybe he sees them as a family, using family assets based on need – I think the finances should be shared (or at least made more transparent) before too long, though, assuming all goes well. Probably a very long shot, but he could even be thinking about not contributing to the house itself (as opposed to family living costs) so as not to put OP in a position of him having a claim on her property in the case of a break-up.
I'm not saying this is especially likely, but it could potentially be the case.
It's so difficult for children when they have to live between two different houses, even though they only effectively get half the benefit of each of those rooms. Meanwhile, one or other of their parents or step-parents are looking at their room standing empty half the time - in no way their choosing or fault - and then resent them for it.
That said, it really does sound like they would be best each selling their houses and then buying a bigger one more suited to their family needs, with 50/50 ownership.