Be wary of a man who does not live with his young children. He either bolted and left them, or she got them away from him. And if you were the one he bolted with - he has a habit and will do it to you.
Do not give up your job, income, savings, pension, home etc to go play unpaid housekeeper to a man who dangles the marriage mirage and maybe baby in front of you … until it's too late for you.
Do not have children with a man who won't marry you, in the hope that will convince him. It won't. He's already got what he wants and you’ll have fewer rights.
Get to know him before moving in together. Learn him before having a child with him. Be aware that the nicest guy can become a nightmare as soon as you get pregnant, or he realises the world no longer revolves around him and his ‘needs’.
Get to know his parents and siblings. They're the eco system he grew up in and he will repeat that. Do you want that repeating itself with you and any children?
The second he first lays a hand on you, or your children, get help and get out. Leaving is the hardest time - but if you stay, this will only get worse.
Keep your own bank account and understand your personal and the household finances. Don't be like the abandoned wife who learned late that water actually has to be paid for because her husband handled all that sort of thing.
If your Spidey senses tell you there is something wrong … there is.
Be careful of suggestions his children come and live with you. You will become a free babysitter, chauffeur, mediator, co-funder etc etc. Are you happy with that?
Be aware that in laws can be a bit bonkers when you have a baby. Set your boundaries, know your rights, practice your ‘no’. No to them watching you give birth, visiting immediately, coming and staying too soon, monopolising the baby etc, if you don't want that, and expect your DP to step up and stand up if you need that.
That's my first ten.
What would you add?