My 5 y/o son seems to know something?

I’m new to this forum but I wanted to share this somewhere. So, me and my mom were talking about when the sun exhausts its fuel and life on earth ending. (I know, not a very optimistic conversation) Anyway my 5 year old son was playing in the same room and was listening but in the moment I didn’t really think anything of it. That was until he bursts into tears and started having a full on panic attack. This is understandable considering he was probably having his first existential crisis. (my fault, didn’t know he was listening) We eventually calmed him down. Then when we were in the car a couple days later he kind of accusingly says to me “you said you would be my mom in every lifetime” as if he was calling me out on a lie now that he knows the earth won’t last forever. I have never talked about past lives or future lives with him, or even much about religion or anything like that. A few days after that when I was laying in bed he climbs in and says “when you die, are you still going to wait for me to finish my life here before I’m not real anymore?” I was thrown off and didn’t really know what to say but he would not stop asking until I promised to wait for him, even though I wasn’t exactly sure what that meant. Another thing he has said off and on since he was much younger, even before the existential crisis, is telling me that he is my dad. And when I tell him “no you’re my son”, he just laughs and says “I’m your dad”. I have never known my bio father or anything about him.
After all of this I remembered something else he said to me when he was about 3. He was telling me about his adopted children but when I tried to ask more questions he kind of just changed topics (as 3 years olds do). However now he constantly talks about his plans to adopt lots of children when he grows up, which is great but I have no idea where he got the idea from as we don’t really know anyone who was adopted and I haven’t really had any convos about adoption with him. (The topic just hasn’t come up)

I just think it’s interesting to hear about children who seem to remember things from a possible past life or even from a limbo period between lives. My aunt told me that my cousin (her son), when he was little, used to talk about missing his wife. And told her that he and his wife were in a terrible car accident and that he didn’t make it but he wasn’t sure if she made it or not, which seemed to really worry him.

If anyone has any insight or stories like this I would love to hear more