Author does not know that there is a difference between a blood familial relationship and a political-legal relationship for inheritance purposes. Tristan, Ruslan's Dad, is not Evan's grandfather. Ruslan is not Evan's Father either. Evan just inherited the future responsibility of Hatra city. There is no blood relationship, Julia is not his mom either. Inheritance acquisition is not the same as being "adopted" and being adopted is a direct legal relationship. Even if Ruslan adopts Evan, Julia has to adopt him too, and that does not mean that the rest of their two families have a familial relationship to Evan. Evan is from another world with other blood-family.
Evan goes back a thousand years, because of Miraya, the sword, but Evan does not impregnate the Crimson Dragon, Valerra, nor does he save her from the curse a thousand years back. I actually thought Arnold Schwarzenegger, would have to protect the hatchling dragon in the future volumes of of this isekai-fantasy novel series. Well, just because author, teleports, time-travels, and all of the rest of the huge unexplainable things that happen around Evan, without any consequences or necessary explanations.
Evan's harem retinue is about to get it's first six-pack from just two intimate relationships at the beginning of Volume 2. Not that the sex or the harem are necessary in a fantasy-novel series like this one.