Petal,
I'd agree with your point of "she never gets any weekend time" if the OP was expected to check into a BnB every weekend so her DP could play house with his kids. Only she DOES get weekend time, it's just that he's a dad, so his weekend time includes his children. That does not automatically exclude her.
That is the point people are trying to make.
Put it this way - I'm a parent. If I, for whatever reason, had to only see my DC for 3 days a week from now on, you can guess which days I'd pick.
Maybe the kids mother works on weekends and can't have them then? Maybe she's not able to provide them with appropriate care at weekends? We're not getting the whole story.
What we do know, is the OP resents the kids. She wants her DP to make an effort and put in quality time with her, without the kids.
Unless there is more to the story (do the DC have special needs, do they not WANT to spend time with their DM... Maybe the Dad is the only adult who actually wants them around? Do the really never go out with their friends or have hobbies on weekends?) it really seems like there is no way tobresolve this so everyone is happy.
Also, those of you who like counting days... Let's say this situation stays as it is for the next 5 years. 52 weeks a year, 3 days a week. OP misses out on 780 weekend days in total, over the next 5 years.
I think it's safe to say the kids won't be around all day, every weekend for much longer?
How old do we think the DP is? 40? By the time he's 45, they're "even". She'll have had as many weekends all to herself as the DC did, if she chooses to suck it up.
And then... She'll have maybe 30 more years? I genuinely don't get it. The DC are only children once. Unless he's planning on spending every single weekend for the rest of his life with the DC, why is this such a problem?
The only sympathy I have, is trying to imagine spending every single weekend with someone I don't like very much... Let's say, DH suddenly decided that DMiL will spend weekends with us for the next 5 years? I'd wonder what has gotten into him, maybe send him to chat with someone, but if he wasn't prepared to compromise, I'd probably move out every weekend for the next 5 years. (I'd insist on taking our DC with me at least every other weekend, but all those other times.... Oooh, I'd enjoy the peace!) 