Actions speak louder than words. I think anyone who has no experience raising children are terrified by the responsibility, even expectant 1st time parents are terrified they are not ready or will not be good parents. Compound that fear with not having gone through pregnancy, birth, rausing from infancy, not having the advantage of learning as you go. I think his fear is natural and warranted. I would look more towards how he is around yourchildren and how your children feel about him. When he is around is it tense or natural? If he is good to you and good with your kids, i think just take it slow and see if your relationship is griwing towards being a family unit. Talk to him and reassure him that there is no rush for him to jump in with both feet and be "daddy". But be mindful of little signs too. Is he truly trying to engage with your kids or does he seem to just tolerate them being there cuz he wants to spend time with you? Ie. Does it seem like he is anxiously just waiting for time alone with you, goes through the motions but doesnt actually light up til the kids are a sleep? Honestly, he is the only one who can decide if and when he is ready to be a dad. Dont push, just observe objectively and really ask your kids, in an age appropriate way, what they think. Children have an amazing way of seeing things adults might not. Good luck! I hope everything works out. Keep writing, someone will always be here