I think the disrespect factor would be a big deal for me. By keeping his life with his ex and baby a secret, it disrespects the role and opinions you have. This seems like a pattern you will experience with this man. Someone who can flake on his own baby for so many years and after some sentimental messages, he is having fantasies of reuniting with them? There is no self-discipline or maturity in this man. Whatever you decide, please don’t ignore the red flags.