The question is if it's the bloodline or MC being a reincarnation/vessel of something else. When he first meets Idriel she says "This time... it'll be the right one", so either she sees him as a returning character (thus reincarnation/vessel) or she saw others from his bloodline try and fail. The second option feels like a stretch to me, so even though having a returning mother who is not human sounds cool, my money is on both parents not having any significant role/appearance.
Another thing is (also probably mentioned before
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) that MC could be another Founder. That's why Idriel recognizes him as a reincarnation, Founder (as a hologram) also immediately notices MC, and the words "break the cycle" might mean that there's a cycle of Founders being replaced by another one and so on and so on. "founder" in this case would be more of a guardian role, but both him and Idriel+NPCs can't break free from the cycle and must remain in their role/world.
I know, there's shitload of things that contradicts it, but I saw tatoo of Uroboros on Founders chest immediately after hearing Idriel's "This time... it'll be the right one" and it simply sprung this theory