The real world equivalent of Obi-Wan’s situation is that it took a lot of convincing for a reluctant Qui-Gon Jinn to adopt him. Years later as his adoptive father is helping him to graduate, he all of a sudden adopts a new kid he just met. Obi-Wan’s slightly hurt, but he can’t complain because he’s about to graduate and move on in his life, and this kid needs help, too. Then their adoptive father dies and Obi-Wan is now the legal guardian of his new little brother right after graduation.
I don’t blame Obi-Wan in the slightest if at any moment he didn’t want to train Anakin.