Is ex's request reasonable? Splitting house

[Itsprincipal]

I'm trying my upmost to be sympathetic here but feel like we're being screwed over.
I met and married my husband 4 years ago, he has 2 children (now 16 and 18). He had been split from ex (never married) for 3 years when we met.
He has continued to pay the mortgage in full as his ex stopped paying when we married.
Now we are looking to move on and get a mortgage of our own, however we are in catch 22.
Ex wont sell, nor buy him out.
We can't get a mortgage until he's released from current one. She has us both over a barrel. We live in a very small 1 bed, and ex lives in a 4 bed with 2 teens. We've suggested she downsizes but she's not having that either.

Thoughts please, I don't want to be unreasonable but feel our lives are on hold

He goes to court. Presumably they haven't got a financial order when they got divorced? So now he need to go to court and enforce the sale of the property.

Get a solicitor and get a court order for a sale .

Is the mortgage only in his name? If it is she can't stop him selling. If hers is on it too she needs to pay half or sell. Surely they will have a tenants in common agreement since they weren't married, court to force sale if she isn't paying the mortgage.

It clearly says they were never married

Is the property in their joint names?.

Court forced sale. BIL wasn’t married to his ex, though they were together for 15 years or more. She didn’t want to sell as wanted to buy him out with new partner, but couldn’t afford to. It dragged on for years. In the end, didn’t have to go through the courts, but it was the next step.

Particularly as he’s paying the mortgage, it’s not sustainable forever. Could you buy her out and then sell? It would certainly make it less complicated than a court ordered sale while she’s living there (went to a viewing as a buyer of a court ordered sale and it was tense).

He needs to go through a solicitor and maybe court if necessary

Completely missed that!! Sorry.

Thanks all, we really don't want to put kids through this.
Mortgage is in both names but she stopped paying so in order to keep credit score, we pay the full mortgage.
I just can't see a way out and thinking what she's doing is a form of control

Put the kids through what? It's a straight forward property settlement, it's not like a nasty custody battle

They are 16 and 18 old enough to understand and makes choices.

legal advice and court

It might sound daunting but it sounds like the best thing to do. Get the ball rolling and see a solicitor.

This!

Just get a court ordered sale - apply via a solicitor.

Presumably having to move out of their home?

Even the youngest one will be an adult by the time the sale goes through.

Just got to explain it to them in a young adult age appropriate way. They'll be fine. It won't be the last time they experience some disappointment in their lives.

Surely tho you’re not putting the kids through anything .. their Mum is ?!
They are old enough to understand that .

Court and a forced sale, assuming in both names.

Or he could move back in, fairly nuclear option, I know...

Or he could stop paying the mortgage. Is he also paying maintenance (ie mortgage payments in lieu of maintenance?). If he is I'm sure he can use mortgage payments as payment.

He can get her out, it's just gonna take balls and nerves of steel. I'd be mightily pissed off that this has been going on for 4+ years op, aren't you?