NAH. If your relationship was close enough to discuss not having kids in the first place, asking out of concern and slight confusion makes sense. I'm bipolar. Kids are not in my future. Your cousin probably feels that he can raise kids after making such an improvement, and has that much faith in his fiance, I can understand it. He sees it as an actual possibility now and is thinking about it, because it means a lot to jer and their future. And dreams can change. At our highest we believe we can do absolutely anything. At our lowest we feel like we will destroy and fail everything. It's exhausting. Your mind is constantly changing and shifting and decisions change with your mood and brain chemistry.

He's not wrong or TA for wanting kids now. And he may be a good dad. Who knows. You're NTA for asking why his previous reasons didn't matter anymore. Changing your mind on a huge decision suddenly would make anyone ask what happened. And you didn't tell him it was a bad idea and not to do it. You're good. Just keep loving and supporting him. Maybe mention you were just surprised by his change of mind, but you're happy for him and hope he has a wonderful future. He may change his mind 5 more times, you never know.