Two profiles

From the old offline profile and onto the new online one.

Hi JosefLBohorquez

Thank you very much I was nervous about deleting one of the profiles in the Xbox Series X console Xbox accessories Tab. I was nervous if I did this it would caused problems. Thank you very much. Have a great day

It's not possible to merge accounts.

Achievements are linked to that profile, but good news, if your kids really liked getting them from the games they played, they get another opportunity to get them all again on their kids account. Woo hoo! At least that's what my son says when he has
to play again when not playing on my profile.

At this point I would recommend designating your adult account as the primary on the machine and then creating him a new account as a child account where you can set permissions and so forth.