How do you coparent?

[Ifyoueverchangeyourmind1]

My ex is driving me insane.
He left ages ago for OW, as far as I'm aware they are still together but not committed ie living together or allowed one another to meet children.

What is driving me mad is his neediness.
At the beginning of our break up he had no care for helping us start our new lives in fact, he was half hoping the children and I would skip down the garden path into homelessness quite happily !
He argued about money, about how she was the one and how he had never had feelings like it.
He even put up a fight over Christmas Day and how he only wanted an hour with them in the morning !

This year he has been in and out of our lives to different extents and at one point trying it on with me. I was slightly childish and told his OW what had happened a series of texts he had sent me but he made out I was crazy and deluded. I blocked him completely and don't engage in contact between visits ( he wasn't bothered about calling or texting about the children it was always general chit chat)

But every time he comes to get the children he spends ages here, he'll drop them off and spend ages here and ask me along to day trips or to go out with him and the children.
Because he's not actually being an idiot I feel bad saying no or that he can't come in because the children are happy to share there home or there time with both of us.

I also wonder how his Girlfriend feels about him spending every other weekend out with us all and "pretending " to be a family !

Currently he is incensed to have a big birthday party for the children and invite all of our family and friends but this unsettles me.
I don't think he wants me back I just don't understand his motives.

[pallasathena]

He's keeping his options open just in case the other woman gives him his marching orders. Sounds like he's used to having masses of attention from you too. Avoid!

[Underthemoonlight]

He sounds as if he's trying to get his feet back under the table. I would brush all these suggestions off