He needs to grieve and focus on his kids.
My best friend was widowed at 31. Her dh also my best friend was 32. I had known her dh first, and lived with him as roomates 12 years prior. He meant the world to me. They will always be my family.
There is an amazing book by Joan Didion called the year of magical thinking. That first year they tell you not to make any major decisions.
I don't know what it's like to be widowed but I know what it's like to see people I loved most suffer, and losing him destroyed me as well in ways.
I've also seen Kat have to rebuild her life with her young dd.
He should not be introducing you to his kids. He should not be meeting your kids. Even if he wasn't widowed it's too soon.
His kids have gone through a serious trauma. You can't fix him or his children.
He needs to focus on them. I don't think he's lying to you, but I think he's escaping into a fantasy life with you. Dreaming of a family with you is a lot easier than facing his own heartbreak and his children's trauma.
If he is the one and this is meant to be, it will work without it being forced.
My advice would be to step back for now and revisit the relationship later on. Take a few months for him to focus on his life and you focus on yours.
It will work out if it's meant to.
If he's not in therapy he needs to be as do the children.
You are not dealing with a rational man, because no one is rational in the early stages of grief.
I have pics in my condo of Will and Kat getting married, pregnant, with their dd. I still miss him like crazy and it's been 13 years. He was the best man I knew.
3 months to be dating is no time at all, especially given he has traumatized kids to focus on.
Big hugs xx