Is this a massive red flag?

[NameChangeTadaa]

I've been seeing someone for 3 months now, he has been separated for his ex for 12 months (9 months when we met so I appreciate it's not been that long).

He has 2 children from this previous relationship aged 2 and 4. I don't think he has told his children or ex that we are seeing each other which is fine by me as it's early days and wouldn't want to involve the children for some time, until we knew it is something solid.

Last night he came round for dinner at mine. I had already begun cooking when he arrived and he was not there for 15 minutes before he got a phone call.

I could tell by his face that it was something he didn't want me to hear and he quickly stepped out into the garden to take the call but left the back door slightly ajar so I ended up being able to hear everything anyway.

It was his ex calling asking him to go round to hers to drop a thermometer off and he replied to her saying he couldn't as he was in the pub and had had a couple of drinks so couldn't drive.
I could hear her shouting at him telling him she really needed the thermometer and he said okay fine. He came back in and told me that he had to leave to drop the themometer at hers. I said okay, what time did he think he would be back as dinner might still be okay? He said he wouldn't bother coming back as he'd probably stay and put the kids to bed and off he went.

I don't know what to make of it really. Mostly I'm hurt that I'd put effort into making dinner for us both and had bought ingredients for it to be wasted and the fact that he didn't want to come back and spend time with me. But on the other hand I understand that he has children and they will come first. But I think it's the lying that I'm uncomfortable with. Perhaps he lied as he hasn't told his ex he is seeing someone. But I just wish he had said he was about to have a meal with a friend or something. Or at least made the effort to come back.

Is this a red flag? Is he not that into me/ not over his ex yet?

He did text me later that evening saying he was sorry and hoped I wasn't angry at him. I replied saying I was a bit upset but I hoped his children were okay. He said they were fine.

Years ago, I got involved with a man who was separated (and had 2 children - both tweens). His relationship with his wife was pretty bad (I heard the shouting phone calls, etc), although he was the one who'd left her so slightly different to the OP.

I fell so hard for him (despite trying to keep my guard up). I loved him more than any man before (or after) but months in, the stress of being away from his children and not being part of their daily life (he had them EOW) was too much for him and we broke up as he just wasn't able to handle a serious relationship on top of everything else. It broke my heart into a thousand pieces and I ended up taking a job on the other side of the world to get away from him. (I highly recommend this btw, it did wonders for me!)

I saw a psychologist a few times as I was such a mess emotionally/mentally and he gave me the best advice ever. And now I pass that on to you OP:

DO NOT GET INVOLVED WITH SOMEONE WHO IS EMOTIONALLY UNAVAILABLE.

It will not end well for you. He isn't emotionally available. It's too soon for him. Get out now before you end up as hurt as I did.

Love the armchair psychologists on mumsnet lol

OP, trust your gut. I distinctly remember a night I was meeting someone I'd been with for a months, and in the final throes of putting make up on for big night and being ready to be picked up when i got a phone call saying his ex had called saying he youngest was I'll and wanted him. He cancelled and i remember thinking, is this what i signed up for...
However i then put myself in that situation and decided if my son was I'll and wanted me, I'd be right there, and to be fair, the fact that he cancelled on a night out to mop up child puke showed something about his character. That was 7 years ago and we are extremely happy together, the two families have merged well and over not a doubt for the future. You need to decide what your cut off is and if hes worth it. Young kids do get I'll, there will likely be more cancelled dates but some fellas are worth it x

Please ignore my earlier reply, it was intended for another thread.