Can we be a blended family?

[Mum112233]

My partner of 12 years has 3 great children (17, 22 & 24) and together we have a 6 year old and a 3 month old. For 10 years he had his older children every weekend from Friday 5pm to Sunday 5pm but for the last 4 years he's had them every other weekend which they aren't happy about.
This changed for a number of reasons but the 2 main reasons were 1) him working all week then being a taxi all weekend to his older children meant we never had anytime together and he never saw our child 2) that we only have a 3 bed house with 1 bathroom and it is far too small for 4 adults and 3 children. We can't get anywhere bigger because we simply don't have the money. We give their mum £700 a month 'child maintenance', pay their mobile phone bills, they always seem to need toiletries/ clothes when with us so we buy them and my partner pays for their days out and food at the weekend so financially we support them more than is required. This often leaves us with nothing to spend on our 6 year olds on our weekends but it was fine as I thought as they got older they would start to be more financially independent but thats not happened.
I don't have an issue with him having them everyother weekend but he leaves home to pick them up at 9am and comes home at 8pm when he's dropped them off. He does this Saturday & Sunday and me & the younger ones are just left all day. I know its hard trying to do things with them all because of the age differences but my 6 year old is now struggling with it, he misses out on friends parties because I can't take him and his dad isn't here ( I can't drive for medical reasons). It's all very strict with their weekends, we aren't allowed to switch any so my partner misses our birthdays etc but if father's day or their birthdays fall on our weekends then he goes to be with them. My partner tries his hardest to keep everyone happy and I understand he's in a difficult place and he should get to see his children on special occasions.
My point is I just don't understand why we can't just spend time doing things all together at weekends. I thought as they got older and started to drive they would come to us in the week for tea etc and weekends would be less strick, they will only come if my partner picks them up but then they want to eat out which we can't afford.
How can I bring us all together and make weekends easier for everyone?

We have a standing order from our joint account to his ex and its been in place for 10 + years so I know it goes to her, it's for the younger 2.
He takes them to town, cinema etc. They spend 1 of the 2 days at his parents so I 100% know he's telling the truth. My 6 year old often video calls him and he's always with them.

How long are you going to put up with this OP?

Why does he not take your children if he is going to his parents?

My financial order from my ex is maintenance till they're 18, then switching directly to them, the same amount, for their first uni degree, should they do one. Both our solicitors suggested that was the norm.
So that bit is perfectly standard.

And this was presumably in the financial order, so the op and her dh knew about this when they decided to have a fourth and fifth child.

He must earn loads. My ex, average wage £50,000 - £221 per month for two DC’s. ( some deduction for his partners child who lived with them 50%).

His older kids are adults. Bizarre arrangements. He needs to talk to them.

I get money for my dd still at university for her maintenance and to cover her costs living with me but not for my dd that works!

Why should the money go to the one at uni directly if her Mum is still providing her with a hime to go back to?

Her Dad is no longer providing her with a hime taht she can go to whenever she needs, only her mum is doing that. So it’s right that the Dad supports his daughters mum in providing her with a home for as long as she’s dependent. The mothers rent/mortgage didn’t get smaller just because one of her children is at university in term time, nor did her council tax bill shrink.

If you feel like you’d be the baddie for trying to change it, it’s because you would be.